I have created some communities in the past for testing purposes, but I am unable to delete them completely. They always appear in the side panel even though I have explicitely clicked to delete the community.
When clicking on one of these communities, the only thing I can do is to undo the deleting.
Communities cannot be fully “deleted”.
They can only be “deleted” in the sense that they disappear for everyone.
You, as a mod, can still see and restore the community. To get rid of it from your list, you’d have to be unassigned as a mod. I don’t think that’s possible if you’re the only mod in a community.
Workaround: Create a throwaway account and assign that as the mod, then leave.
That is possible.