I'm not a JS expert but have done a little research to attempt to create 2 new tabs: Notebooks and TableOfContents. I've successfully created the two tabs and now want to re-order them in the side bar.
First, to add them to the sidebar, I've added the tag " $:/tags/SideBar" to both tiddlers.
Next, I want TableOfContents listed before the core "Open" tab, so I created a field:value of:
list-before: $:/core/ui/SideBar/Open
This works fine.