Even if there is other stuff that is outdated, one needs to start updating it SOMEWHERE, right?
Apart from that, I would like to repeat: “I work on a Windows 10 machine and when I drag and drop a file into JabRef, it even selects the entry, so all I need to do is press enter or double click to open the entry editor.”. Hence, pressing enter should suffice. Afterwards, just check the {} biblatex source tab. All the imported data is in there. You will not have to switch to multiple tabs if you check that one.
This is the current implementation, so unless somebody feels like working on this and creating a pull-request, this will not change. Sorry I am not big into coding myself, so that’s all I can help you with.