The closest that you could get to this with Juicebox would be to display your gallery in Small Screen Mode (usually used on mobile devices) where thumbnails and images are displayed on separate pages (so that the main images can be given as much space as possible on small screens).

When the gallery is initially displayed, the user will be presented with a grid of thumbnails from which a main image can be selected.
When a thumbnail is selected, the thumbnail page is replaced with the chosen image (and the user can then navigate through the main images).
The user can return to the thumbnail page by clicking the 'Thumbnail' button on the gallery's Button Bar.

You can force a gallery to be displayed in Small Screen Mode by setting screenMode="SMALL" (in JuiceboxBuilder-Pro's 'Customize -> General' section).
Please note that screenMode is a Juicebox-Pro configuration option which is not supported by Juicebox-Lite, the free version.
For reference, a complete list of configuration options can be found here.

All thumbnails will be the same size as each other but you can determine the size via the thumbWidth and thumbHeight configuration options.

More information about Screen Modes can be found in the Gallery Tour.

Here's a demo gallery using Small Screen Mode.

I hope this points you in the right direction.

When Adobe announced the proposed end-of-life for Flash (in this blog entry dated 25 July 2017), they also posted this forum post (on the same day) regarding AIR.
The takeaway from the forum post seems to be this quote:

As far as I am aware, there has been nothing to suggest that anything has changed in this regard since then (with new features being introduced in the latest version of AIR, rather than it being just a bugfix release, which is encouraging).

It is sad to hear that Adobe are dropping Muse from their portfolio but Muse and AIR are two very different products and the news regarding Muse should, hopefully, have no bearing on the future of AIR.

In any case, if Adobe were to ever retire AIR, I'm quite sure that the Juicebox developers would find another suitable platform to provide users with a quick and easy way to create and edit galleries (like JuiceboxBuilder does today).
However, it looks like it may not come to this (at least in the short term, not knowing what might happen over at Adobe).

That's weird. I'm pretty sure both options will call the same function.
At least you have a workaround (use the 'Open Gallery...' button instead of the 'Gallery -> Open...' menu option).

Out of interest, does the 'Gallery -> New' menu option work?

I'm really not sure what might be causing this problem. I still think there's a chance that something might be blocking the 'Select Gallery Folder...' pop-up dialog window from being opened but why this would happen via the drop-down menu but not via the button on the 'Start' tab is a bit of a mystery.

Have you tried my two suggestions above yet (to temporarily disable any security software and manually delete the two folders I listed)?
Also, please try completely uninstalling JuiceboxBuilder-Pro and then reinstalling the application to see if this helps.

You're welcome!

If you really wanted to, you could change the icon used for the Back Button to a custom icon more suited to the page that your Back Button redirects to.
If you'd like to try this, please take a look at the Using Custom Icons support section in the Theming Guide.
The IcoMoon library might have an icon that you could use for your mailing list link, otherwise you could create a new icon yourself.

Yes. There's no need to change the backButtonUrl (the URL associated with the Back Button). Just change the backButtonText to something shorter than "More Pascal RIBEN Galleries", for example "Mailing List".

Your post above quotes a reply I gave to a user in the forum over 4 years ago (in this thread).

Do you have a problem with the WP-Juicebox?
If so, please describe the problem and post a link to your gallery's web page so that I can see the problem for myself and hopefully help further. Thank you.

This is due to your long backButtonText ("More Pascal RIBEN Galleries").
In Small Screen Mode (on mobile devices), the Back Button and Button Bar share the same horizontal space.
Space is reserved for the Back Button and, once this has been displayed, the remaining space is used for the Button Bar (which will wrap within the available space if necessary). This avoids the Back Button and Button Bar overlapping each other.
With your long backButtonText, there is enough space to the right of it (on your device) to display only one Button Bar icon (which is why it wraps to display all the icons in a single column).
If you were to reduce your backButtonText to something shorter (like "Home", for example) or use the 'home' icon (by setting backButtonUseIcon="TRUE"), then the Button Bar would have more space to display icons in a row.

@matthewswift

I understand your desire to try to adapt Juicebox-Pro to do something that you would like it to do (but that it was not designed to do). However, it looks like you may have unpacked the source code and, unfortunately, modifying the source code is not supported. This is noted in the FAQ below:
Does Juicebox-Pro include the source code?

Thank your for posting your suggestion in the Feature Request forum thread, though, where it will be seen by the developers who will at least consider it for inclusion in a future release (although I have no way of knowing which requests will be chosen for implementation).

(Incidentally, I'm not sure what might have changed between v1.5.0 and v1.5.1 to break your modification. Whatever the change was, it would have been made for the sake of functionality rather than to prevent users from adapting the software.)

Thanks again for making your suggestion known.

Just increase the inactivityTimeout value from its default value of '4' (seconds) in JuiceboxBuilder-Pro's 'Customize -> Main Image' section.

Alternatively, you can have the overlay never auto-hide by either setting inactivityTimeout to '0' or showImageOverlay (also in the 'Main Image' section) to 'ALWAYS'.

You could also display the Info Button on the gallery's Button Bar by setting showInfoButton to 'TRUE' (in the 'Button Bar' section) to allow visitors to your website to toggle the overlay on and off (by clicking the Info Button).

For reference, short descriptions of all configuration options can be found on the Config Options page.

It is likely that you have found a post referring to WP-Juicebox (the Juicebox plugin for WordPress) as this plugin has a file named 'config.php'.
However, if you are creating or editing a gallery with JuiceboxBuidler-Pro and do not want the image filename to be used as the image title (which is the default setting), then just go to 'Images -> Titles -> Use None' from the drop-down menu at the top (and then save your gallery on the 'Publish' tab).

@kuwaha

Do you get exactly the same error message as the original poster ("Code: 5100") or a different error message?

If you have not already done so, please try following the procedure noted above (to uninstall both JuiceboxBuilder-Lite and JuiceboxBuilder-Pro and then manually delete all the folders I listed before before attempting to install JuiceboxBuilder-Pro v1.5.1).

Have you also tried the additional suggestions, such as creating a new administrative user account and trying to install and run JuiceboxBuilder-Pro v1.5.1 from there?

If you continue to experience difficulties, please let me know how far you get into the procedure and what error message (if any) you encounter along the way.
Also, please let me know what operating system you use.