I tried every remedy to the icon scrambling problem documented in perhaps a dozen relevant threads. Nothing worked. Then, I tried the export  / import trick mentioned in the prior message. This didn't work either. Not at first. But then a strange notion popped into my head. I added a slight twist gleaned from another conversation. To my delight, the slightly revised procedure worked. Here's the exact sequence of operations:

1. Export the key specified above.
2. Arrange the desktop with appropriately-sized icons in their desired locations.
3. Right click and select REFRESH from the local menu.
4. Import the saved registry key.

Step #3 made all the difference between failure and success.

HTH some of the folks who have struggled with this vexing problem.

I tried every remedy to the icon scrambling problem documented in perhaps a dozen relevant threads.  Nothing worked. Then, I tried the export   /  import trick mentioned in Ben Lavender’s answer.  This didn’t work either; not at first.  But then a strange notion popped into my head.  I added a slight twist gleaned from another conversation.  To my delight, the slightly revised procedure worked.  Here’s the exact sequence of operations:

1. Export the HKEY_CURRENT_USER\Software\Microsoft\Windows\Shell\Bags\1\Desktop key (as specified in Ben Lavender’s answer).
2. Arrange the desktop with appropriately-sized icons in their desired locations.
3. Right click and select “Refresh” from the local menu.
4. Import the saved registry key.

Step #3 made all the difference between failure and success.