Created attachment 154372 [details]
The idea is to arrange all the "settings" stuff on bottom. I will also recommend to have an link to the extension webpage or at least to the extension dialog where you have the link to the extension page.
however styles, navigator has settings on bottom.
(needsUXEval needs cc ux-advice)
While I agree with the tight integration of extensions (the use case for this request, which should be the summary too, is to easily extend the Gallery) I don't like the placement at the bottom.
We discussed this some time ago and came up some proposals at https://design.blog.documentfoundation.org/2015/04/02/libreoffice-design-session-shapes/
it looks like an enhancement...
Created attachment 154473 [details]
Gallery mockup with means to extend
This mockup was done for this blog post https://design.blog.documentfoundation.org/2015/04/02/libreoffice-design-session-shapes/. The sidebar allows to search for items, you can hide categories as known from the toolbar, it has a dedicated section for objects dragged onto it, and - most relevant here - allows to be extended. "Add more..." opens a dialog which lists all extensions flagged as gallery relevant and starts download and installation per click (see also https://design.blog.documentfoundation.org/2016/11/11/additions-to-libreoffice/).