>>I wish we had this 20 years ago...

Yes. I asked Chen how difficult this would be on 14 March 2019. On 17 March, he provided a release with TMPFILES= templates and other fixes, e.g. unpredictable need for multiple attempts to create or erase folders/files under Windows 10. Then I believe he saw this thread with the wish from Thomas for changing TMPFILES= on the fly... and on 20 March he released the version with SYS(9021) to change TMPFILES= settings on the fly. This is why I appreciate working with Chen.

>>I assume the temp files already open remain where they were, and that ALL of them get cleaned up on exit.

Testing was of TMPFILES = %TEMP%\VFPPROCESSID%. The new folder IS created. Tmp files ARE cleaned up on exit, though the folder remains. It's easy enough to remove at conclusion of app if that's going to be an issue, though I believe Windows 10 can do that itself these days. If you screw up your path, tmp files go to %TEMP% as usual. I have not tested SYS(9021) as config.fpw changes provide requested isolation.

>>Where are you taking all those looks?

One always wonders about paths not taken. -- Warren Christopher