As far as I’m aware, there isn’t a way to adjust the caption track height in Premiere Pro.
That said, it looks like something may have gone wrong with your interface. Your caption track is missing a Track Lock and Track Target button. I would suggest trying the following:
Reset your workspace by going to Window > Workspaces > Reset to Saved Layout.
If that doesn’t fix it, try resetting your preferences by holding Alt (Windows) / Option (Mac) while launching Premiere Pro.
AdChoices