To reorder
Put this in a new tiddler and save the tiddler so yo see the tag: <<tag "$:/tags/SideBar">>
Click the tag you see and drag'n drop to reorder the titles therein. This changes the order in the sidebar.
To hide a tab is more intricate:
Go to $:/core/ui/SideBarSegments/tabs - to do this, you can for instance copy-paste this strange title into the same tiddler that you put the tag in and then save that tiddler again - and then click on the link you see.
Once there, you edit the tabsList filter therein like so
tabsList="[all[shadows+tiddlers]tag[$:/tags/SideBar]!has[draft.of]] -THENAMEOFTHETABYOUWANTTOREMOVE"
i.a a minus sign in front of the tab title. Which tab title you ask? You find the titles in the yellow tag where you reordered them.
If it is any comfort I just posted a
request for a small improvement on this matter.
<:-)