Keyboard Shortcut to focus on these windows
I don't know any shortcut, but there is a workaround how you can use keyboard only to focus it. You may enable mouse keys - press 5 times Alt key and then use keyboard to move the cursor.
Alternatively you may install some third party tool to control the mouse. My recommendation goes to Karabiner Elements, because I use it for bunch of other useful staff. Once you install it you should  add Mouse Keys Mode.
There is also https://github.com/h2ero/XEasyMotion   but I haven't used it personally.