I'd like to add a new gallery for UI widgets see extension https://extensions.libreoffice.org/extensions/gui-widget-prototyping there are two galleries one has widget and the second one icons. Both can be used for UI related stuff.
Please share an image here so we don't need to install extensions.
Created attachment 158735 [details] Widget Template
Created attachment 158736 [details] widget extension
My first impression: too many items, not ultimately relevant for an office suite (although some people report this use case). So my take: extension. OTOH, if we get rid of the pointless "Computer" gallery this one makes a bit more sense. See also bug 131308.