currently the only way to do it is to use the “ims_before_galleries” and rewrite the whole gallery markup,
on the next release v3.2.1 there are a new hooks “ims_gallery_navigation” and “ims_taxonomy_navigation”, that allows you to create your own navigation.
This is only the second time somebody asked about it.
If you want to search for anything you need to use the site search it includes items from the forum, post, pages and galleries.