Unable to drag & drop into GIMP when opened from XNViewMP

[W1tchseason]

Hi
My "associated program" with JPEG files is GIMP 3, and when I press F3 in XNViewMP with a file selected GIMP opens (as expected). But I am then unable to drag another file into that session of GIMP - It's as if GIMP has been opened in admin mode (where d'n'd is disabled).
If I open GIMP first I can drag as many files as I want from XNViewMP, but ifI open GIMP by pressing F3 I can't d'n'd at all.
Any suggestions as to why that might be?
Also, what is the difference between "associated program" and "associated editor"? When I press F4 nothing happens - how can I set up an associated editor (e.g. not GIMP)?
Thanks

[user0]

I am then unable to drag another file into that session of GIMP

drag&drop to tools panel

how can I set up an associated editor (e.g. not GIMP)?

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