Ok, hoping someone has seen this or at least knows where to look.

I have been waiting around a bit to upgrade my system to CentOS 8, and actually wanted to wait on 8.2, but had an opportunity this week to actually do the work, so took the opportunity.  Here was my process:

1.) Installed CentOS 8.1.1911 on a spare mSATA SSD in my spare M6700 laptop.  Installed the RPMfusion nVidia drivers, the PowerTools repo, set up the extensions for Places, Applications, etc, and got it prepped to accept my /home disk.

2.) After complete backups, physically moved my /home disk from the CentOS 7 M6700 to the CentOS 8 M6700.  /home is on a LUKS LVM lv; got all the mount options and encryption options setup to start on boot.  All of that now works, even though it took a bit of wrangling (if the filesystem mount is set to start up at boot without the nofail option BUT the encryption option is left at the User Default setting, it will not work!).  Did a complete SELinux relabel (touch /.autorelabel and reboot).   Moved the default GNOME config dirs over to the old /home; don't want a lot of cruft left over from the C7 install (which has been upgraded over the years from C6, Fedora 14, and earlier, and it was time to get rid of some cruft, I'm sure).  After booting back up with the old /home in place, verified the GNOME extensions settings I had set up after the new install. All looks good, and working like it's supposed to so far.

3.) Moved over the Win10 and Win7 virtual machines, all of that works fine.

4.) Started installing my everyday programs, beginning with Harrison Mixbus.  The program put its menu entry in place; all good. However, when I go to double click on the .desktop shortcut, it opens in gedit.  Hmm, this ain't quite right.  This worked fine on C7 in GNOME Standard mode.

So, at this point, the Mixbus_6.0.702.desktop file is on my desktop, it's in ~/Desktop with executable permissions and is owned by the correct user, but right-clicking on it does not bring up the choice to 'Allow Launching.'  The GNOME Extension 'Desktop Icons' is installed and is active.  I've tried a whole lot of suggestions, but wanted to see if anyone here had seen this before and has solved the problem to allow launching of the .desktop file as it is supposed to do.  Just knowing that 'it works for you' actually is helpful, especially if we can figure out what is different from my install to yours (SELinux context, permissions, etc).  Just knowing where to look would be helpful; and I'm going to diff my old GNOME config from my /home backup to the fresh as-installed config....

gnome-shell-extension-desktop-icons-3.32.1-10.el8.noarch is installed.