In VW2019, in the revised title block tool dialogue box, you cannot seem to tab between fields.
This is known issue and should be fixed in Service Pack 1. Until then, here is a workaround:
If you are using Mac OS, could you make sure that you have Settings->Keyboard->Shortcuts->All controls checked for keyboard access, as shown in the attached picture? If tabbing still does not work, try using Ctrl + Tab, instead of just Tab.