The issue has been fixed in the latest release of InDesign – InDesign 2021.
Please update to this new version of InDesign to get the fix.
Adobe InDesign team
An error occurred while saving the commentKyle Kemin commented
I'm having the same problem, I managed to put it into the sidebar but then nothing happens upon clicking it. Please sort this out ASAP, the original issue has been reported over a month ago now...