As far as I know: no, you can't do it at the moment.
But the upside is, the ~/.newsbeuter/queue file is plain text and
contains one URL per line, so you can write a script that'll pull the
last enqueued URL out and pass it to whatever program you need (possibly
erasing the URL after that).
If anyone's interested in working on this, I will accept a patch that
adds enclosure's URL to the end of the URLs list, so that you can use
the following trick:
macro i set browser "your_program %u" ; open-in-browser ; set browser "your real browser"
This will let you pass the URL to your program by opening the URL dialog
(`u`), selecting the last URL (`End` should work) and invoking the macro
(`,i` in this case).
PGP key 356961A20C8BFD03
Fingerprint: CE6C 4307 9348 58E3 FD94 A00F 3569 61A2 0C8B FD03