Coming back to this topic after creating a bunch of galleries with these observations on captions. And customizations.
My wife and I manage our photos in Lightroom. We add captions there and take the additional step of writing the metadata to the base files. This is essential in my view, unless you like losing your work. Tag and keyword the files too. Then select groups of images to go in a Gallery. Use export to put them in an /export/galleryname1 ... n folder safely outside the Lightroom catalog area. Then verify results in Windows file explorer. If you set the view for picture type folders to detail and show the title field you can verify that captions got written successfully.
Now bring up Juicebox Pro. Create a new gallery. Bring in the files from /export/galleryname_n. Now here's issue number one. Unless you have the preset set to have captions use the IPTC caption field at this point, Juicebox will create the files for the gallery without embedding the metadata caption. So, if I create the gallery in a directory /jbox/galleryname_n and look at the folder in windows file manager I see nothing in the title field (which is really the caption field). You can set a preset to use the IPTC caption for the caption and, if you remember to load this first, the files will be created in the /jbox folders with the captions metadata.
This leads to two questions ... which I will turn into feature requests if you confirm this. 1. is there a way to set default preferences that will ALWAYS apply, even to new Galleries and unless explicitly overridden. In other words so that you don't have to remember to load your preset every time. What happens to us is that we occasionally forget to load the captions.xml preset. Bring in the files. Reorder the files by dragging them around in the order we intend for the Gallery. Publish it and notice that captions aren't there. Since Juicebox has not created files with captions metadata we can't just reread the files after changing that option. And 2. which is not so much a question as a request for confirmation. The files created for the juicebox images directory, if captions are off in presets, don't include metadata. It would be really useful if they did, so you wouldn't have to delete everything and start over, including dragging the files around into the right order all over again.
In other words, the refresh that you mentioned in your 2016-06-24 response only works if Juicebox has copied over the image files with caption metadata and as far as I can tell it doesn't do that if captions are "off".
It would also be helpful if you could shift-click or ctrl-click the list of images in a Gallery in order to delete them. Again, I'll consolidate this into a feature request if there is no work around for this.