Very Slow return to Editor after debug run

I’ve a program that creates a large number of objects (a maze forest). The creation process takes ~28 seconds but when I click the arrow to return to the editor, it takes >8 minutes. What exactly is happening that takes so much time? Is there any way (short of a force quit) to speed this up?

Just tried something that has made a major difference. All the trees were imported as Generic & with Animations. I dropped these and cut my map size by a factor of 2. The factor of 2 had the expected change to set up times but the removal of the Animation components from the trees seems to have made things a lot faster.