Shortcut to open file from nautilus with 2nd default App in GNOME?

Hello.
I find myself handwriting into pdf files very often with xournal, but I do not like to change the default app to open a pdf file away from the pdf viewer.

So I wonder how one could devise a keyboard shortcut that opens the currently selected file in nautilus/“Files” with the application of my choice?

I know about the custom shortcut feature under GNOME settings and I used it to invoke a shell command to toggle the touchpad. But accessing the current selection from nautilus is beyond my knowledge.

Thanks for ideas or pointers.

Best