Here are a few tips which should hopefully help to clarify a few things.

If you create a gallery with the Lightroom plugin and then edit it in JuiceboxBuilder-Pro to create a multi-size image gallery, then the images that Juicebox will have to work with are the images in the gallery's 'images' folder. When resizing images, JuiceboxBuilder-Pro scales down large images but does not scale up smaller images so if the images in the 'images' folder are already smaller than the maximum image bounds for the specified image sizes, then they will simply be copied across to the gallery folder as they are without being upscaled. Therefore, make sure that Lightroom exports images large enough that they have to be downscaled by JuiceboxBuilder-Pro.

When displaying a gallery in Large Screen Mode, Juicebox displays the Medium size images in the standard gallery. Large size images are reserved for use when the gallery is expanded fullscreen (via the Expand button on the Button Bar) and for when an individual image is opened in a new window (via the Open Image button on the Button Bar).
For more information about Screen Modes, please see here.
For more information about Multi-Size Image Support, please see here.

When a gallery is displayed by Juicebox, the images are scaled within the gallery's image area according to the imageScaleMode configuration option (found in JuiceboxBuilder-Pro's 'Customize -> Main Image' section). By default, its value is SCALE_DOWN. Images larger than the image area will be scaled down (respecting the image's aspect ratio) but images smaller than the image area will not be scaled up. Alternative values for this configuration option (and short descriptions of each) can be found in the Main Image section of the Config Options page.

Images within a Juicebox gallery will only ever fill the image area within the gallery. If you want your images to cover the entire screen, you will need to disable gallery elements for which space is reserved, such as the thumbnails and make sure that other elements such as the caption area, the Gallery Title and the Button Bar are either disabled or displayed on the overlay (rather than in positions outside the image area). You may also need to set imageScaleMode="FILL" (although this will crop images unless their aspect ratio matches that of the image area).

The Pro Options section within the Lightroom plugin's interface is a text area where Pro Options can be entered as text in the form optionValue="optionName" (e.g. autoPlayOnLoad="TRUE").
Please see the Alternative Methods to set Pro options section at the foot of the Lightroom plugin's support page.

None of the Juicebox plugins are as fully-featured as JuiceboxBuilder-Pro (which comes with Juicebox-Pro and has individual controls within its interface for all Pro Options) and they are provided as a convenience for users who already use programs such as Lightroom and want to be able to create Juicebox galleries within their existing workflow.

It is actually quite a quick and easy process to open a gallery (created by the Lightroom plugin) in JuiceboxBuilder-Pro, customize the gallery as required and re-save the gallery.
You could even create a preset in JuiceboxBuilder-Pro so that you can quickly apply a collection of configuration options to an existing gallery in a single action.

It is not possible to change the share URL sent to the social media networks. This data (using the actual URL of the web page) is created by the 'juicebox.js' JavaScript file which is packed and obfuscated and cannot be modified.

The code you refer to is the code which is dynamically generated by Juicebox when the gallery is displayed.
This code cannot be changed. It is generated by the 'juicebox.js' file which is packed and obfuscated and cannot be modified.

The code you refer to is not the code that is actually on the web page which can be seen when viewing the source of the web page in a browser (or when opening the web page in a plain text editor).

If you want to include SEO content code in your gallery's web page, then create your gallery with JuiceboxBuilder-Pro and select the 'Add SEO Content' checkbox in the 'Customize -> Sharing' section.
Please see the Search Engine Optimization support section for further details.

When opting to 'Add SEO Content', code such as the following will be entered into the gallery's 'index.html' page for each image.

<p><img src="{Image URL}" title="{Image Title}" alt="{Image Caption}" /><br>{Image Title} {Image Caption}</p>

You can change the color of the text shadow using the textShadowColor configuration option in JuiceboxBuilder-Pro's 'Customize -> Color' section.
However, you would have more control over the text shadow of your image titles and captions using CSS such as the following:

<style type="text/css">

    /* Image Titles */
    .jb-caption .jb-caption-title {
        text-shadow: 1px 1px 1px rgba(0,0,0,1);
    }  

    /* Image Captions */
    .jb-caption p {
        text-shadow: 1px 1px 1px rgba(0,0,0,1);

    } 
</style>

The sample code above sets a black shadow close to the original text and with a very small amount of blur which sounds suitable for your scenario.
For more details on the parameters of the CSS text-shadow property, please see here.

I'm glad you've got it working!
Thank you for posting back to let me know.

In order to open an existing gallery in JuiceboxBuilder-Pro, you need to click 'Open Gallery...' (or 'Gallery -> Open...' from the drop-down menu at the top) and then navigate towards and select the gallery folder itself (not a file) before clicking 'Select Folder'. The gallery folder is the folder which contains the gallery's XML file and the gallery's XML file must be named 'config.xml' (if you have renamed or moved this file, the gallery will not be able to be opened by JuiceboxBuilder-Pro.)

Thank you for reporting this problem.
It looks like a bug and, unfortunately, there is no workaround that I am aware of (other than to not set randomizeImages="TRUE").
I have notified the developers and hopefully this can be fixed for a future version.

Some imaging programs such as Adobe Photoshop have the ability to read the EXIF orientation flag and display the image in the orientation specified by the flag but other programs (such as JuiceboxBuilder-Lite) do not read EXIF information and just display the image as it is.
Unfortunately, there is little consistency, even between different web browsers.
If you are having problems with the orientation of a specific image and view it directly in Mozilla Firefox, (if you drag and drop the image into an open tab or window), you will likely see your image displayed in a different orientation than if you were to open the same image in Google Chrome.

Unfortunately, no matter what decision is taken regarding EXIF orientation (whether or not to use it at all and, if using it, how to interpret it) there seems to be no single solution which will work for everyone.
This link (whilst a little out of date now) certainly makes for interesting reading.

The only way to ensure that your images will be displayed as you expect in all browsers and programs would be to strip the EXIF information from the images (by re-saving the images in an imaging program and choosing not to keep the EXIF information) and then rotate your images until they visibly look correct.

However, JuiceboxBuilder-Lite does have the ability to rotate images on the 'Images' tab (see the 'Rotate' arrow near the lower-right corner of the screen in the first screenshot on this page) so you can rotate images within JuiceboxBuilder-Lite without the need to re-save them without the EXIF information first.

I hope this helps.

If you set imageNavPosition="STAGE", then the image navigation buttons will be positioned relative to the stage (regardless of the size and position of the image). However, if the image is large enough (and of the correct aspect ratio) to cover most of the image area within the gallery, then the image navigation buttons may be stacked on top of the image. Space is not reserved for the navigation buttons. You could perhaps compensate for this by increasing the imagePadding (in JuiceboxBuilder-Pro's 'Customize -> Main Image' section).

Yes. Sliding works only with adjacent images using the main image navigation buttons. When clicking thumbnails, images fade in and out.

It looks like the problem may be with your indexPageName="new index" entry.
Try changing it to indexPageName="new index.html".