After edit window dispeared.

I just went through the effort of redoing all of my toolbar customizations. But that does sound like a handy trick I'll have to remember. 

Completely gone. Searched high and low and closed everything but PC-DMIS and still couldn't find a trace.

I was told it showed at background.  So you can not find it and have to rename the corrupted file.

Can you try the following..

• Shut down PC-DMIS.
• Launch the settings editor for the version of PC-DMIS you were running.
• Click "CONNECT" and wait until the settings populate.
• Click "FIND" and then type "DialogFixedPosition" in the "find what" box before clicking "find next".
• Change the "current vale" to 1 and then click "Save"
• Close the settings editor and re-start PC-DMIS

That should reset all dialogs back to their default position instead of remembering where they were positioned the last time they were accessed.  I'm not sure if this also applies to the edit window but it's worth a try.

PC-DMIS Help Center - 2023.1 (hexagonmi.com)

I'll definitely try that the next time this happens.