I can only add one subtitle/caption, then the "+" add new subtitle features disappears

I had to add some closed captions to an existing video to export the SRTs, to discover that Premiere's CCing workflow has completely changed. I found some tutorials on the new flow, so went about adding captions.

Or, rather trying to.

After I add the first caption in a project, there are no more feature buttons for adding more. I can add one caption, and that's it. Then, the text panel just shows one caption, and nothing more to be, or can be, done. See screen below.

NOTE: there are 2 captions in my screen shot, but that's only because I had to resort to copying and pasting the first one over and over again, across other timelines as well, to create the rest.

I googled this, but no one else I can find seems to be having this problem, which leads me to wonder if I've just missed a setting somewhere and it's so glaringly obvious where it is, no one ever mentions it in a tutorial. I've gone cross-eyed looking for something, but I guess I have a blind spot.

What am I doing wrong?