Greetings, ParisTexan.
I see that you're unable to change the size of the MiniPlayer in the Music application on your Mac on macOS Catalina. The default size is larger than you want to use, and I'm glad to help with this.
Use Music MiniPlayer on Mac -- Not only can you hide large artwork or the Up Next queue, you should be able to drag the sides or corners to resize the MiniPlayer.
How to use safe mode on your Mac -- If you can't resize it using the sides or corners, restart your Mac in safe mode and see if you can adjust the size of the MiniPlayer in Music, then apply the steps provided referring to the information below:
- If the issue happens while in safe mode, follow the steps under "If the issue continues in safe mode".
- If the issue doesn’t occur in safe mode, the steps to use are under "If the issue doesn't continue in safe mode".
Let me know how that goes.
Take care.