On the individual slide index pages, I would like to place words next to the navigation buttons to describe their function.
The tooltips that appear when the visitor hovers on them are always sufficient. Anyone who has used the internet in the last decade knows what most of them mean without being told, and once he's clicked on one of the more obscure icons, he will immediately get the idea. Loading up the navigation controls with text is a visual distraction, and also makes it impossible to view the album properly on a phone, where all that excess verbiage can't be shoehorned onto the display.
On the Thumbnail index page, I would like to insert a text link to return to the main table of contents page.
Any of the skins I've mentioned above provides a simple way to do this without doing any coding or editing outside of the skin's own user interface. The UI is a little different for each, but look for
Code > Top Info. That can be used to plant some text above the table of thumbnails, which you can enter as:
<a href="https://example.com/">Click here to return to the home page</a>