thanks for your quick answer!
I forgot to add that you might need to reset the keybindings in the dialog and restart JabRef afterwards.
The problem with the font size should be solved in this snapshot (if you are in an entry editor field, the entry editor navigation is done, outside the font size is triggered)
However, the keys only work if you are in an entry editor field, e.g you first have to click in one field.
I mean that I would like to do CTRL + E (edit entry) and then CTRL + TAB (tab navigation).
This sounds like a good idea. I will see if we can make it possible to focus automatically the first field in the tab