Inventor Fusion

[#1]

I was able get to a Restore Point created a couple of days ago and that problem is solved.  I will try to get back to your problem on Monday.

It looks like I discovered a serious security problem in Windows. 
At work our machines have a program called Deep Freeze that returns the computer as set up by IT each time it is rebooted, so I can safely test things like this.

Turns out if you save even a MS Word *.doc file (can be blank) to the desktop and then rename to *.stl it causes Windows Explorer to go into a failure loop. 

Only discovered this because I thought you renamed an stl in order to attach it here since you can't attach stl directly.

[#2 · Accepted solution]

Getting back to the original problem, Fusion is not the tool you want it to be.  As posted earlier, Fusion is a solid modeller, Blender is not.  Blender is a mesh modeller - so if you want "like for like" comparisons, download 3ds max.  That will give you all the push/pull mesh modelling tools you can imagine (and a few more).  It supports STL files too (unlike Windows explorer apparently!) 

[#3]

Thanks. I'll look into it today.