In another post I described some difficulties and changes in what file extensions could be previewed in Windows File Explorer.

I had a 2020 version of PowerToys.

An information link to powertoys:
https://learn.microsoft.com/en-us/windows/powertoys/file-explorer

Over a 150 file types are covered.
I think NOT .3dm. (?)
There is also talk about Outlook conflict.
There is also talk about "overriding" existing preview handlers.

There is a list of preview handlers in the Windows registry. (Still to be studied)

The latest Windows 11, and even latest Windows 10, have DIFFERENT menu structures than are describe in various internet "Cure" procedures.

There seems to be some problem with OneDrive "wiping" out thumbnails of .3dm files(?)

Running programs as administrator seems to have many methods eliminated(?)

I spent several hours today looking up Internet topics regarding File Explorer, and Preview.
Due to my continuing ignorance, I cannot make any recommendations.

I do not know how I broke my .js and .htm views, and partly broke .3dm views.
Viewing files on external SSD's seems to be harder(?)

So Rhino and MoI have different .3dm viewers...

- Brian