OK so I have found a new annoyance with Catalina and it is in the save dialogue box.
Often when I am rendering something in After Effects I overwrite an old render with a new one. But when I make the file, it adds a _1 to the filename, so I open the save dialogue and hit the right arrow to go the rightmost character and delete the two characters. Before Catalina that is how it worked, but now it goes to the end of the .mov so if you delete, you delete the .mov instead of the last 2 characters.
This is a new behavior, and completely changes how I have worked for years. It is a huge annoyance!