Even on the enemy confrontation, the NPCs wont spawn until you click continue. So you can just downsize the window and do as you please.
I suspect THIS is the reason they call you the Grand Nagus! Always finding ways to maximize profit...
I do have a sneaking suspicion that this trick doesn't work 100% of the time but in that case they usually don't spawn on top of you - unlike a few Borg ships I can waggle my finger at... (this is to my memory which I do not claim to be faultless)
Yeah I do this too. As mentioned, the scan 5 anomalies missions are very nice for this. I also like Aid the Planet missions. They usually have 4 anomalies, plus I can get DXP and some pocket change from selling the item they give me. The only ones I abandon are enemy confrontations in space. For things like base investigations however, I just snag the anomalies and then warp out. Seems to work very nice for me.
If you truly want to abuse the system, keep the missions. Just leave 'em. It'll create a nice bunch of boxes on the right side of the screen. Then just go from mission to mission, looting the anomalies and leaving them long enough for the server to dump the map.