This was so weird that I have to report it.
I was adjusting the Sizes in the ControlPanel Theme Tweeks area and at one point my SideBar became completely unresponsive. I could not create a new tiddler. I could not open the Control Panel again.
After scrutinizing my file system for permissions issues and finding none (it is a node tiddlywiki), in a desperate attempt to recover my wiki I imported the $:/ControlPanel into the non-functioning wiki from one that was working normally. After resetting the sizes (Story right, Story width, Tiddler width, Sidebar breakpoint, and sidebar width) to match my functioning wiki, I was able to recover the sidebar function again.
I don’t know how or why this happened, but I thought I would throw this out there so you gurus could speculate and educate the neophytes like me.
Cheers