I just discovered that if I am in the /admin path (and only in the /admin path), I can see (in the left side menu) the Categories as well as the Tags, and both are collapsible in there (functioning correctly).
However on any path other than /admin/* I see only the categories which are not collapsible. I don’t see the tags at all.
Also, when I am in /admin/* and I have expanded the Categories there, then they also appear expanded on the front page and in paths other than /admin/*
But still, when I have the Categories collapsed in the /admin/* path, then I see only the word Categories in paths other than /admin/*