I am also just starting with Ubuntu 20, many new amazing things work out of the box but the Desktop behaviour feels indeed "experimental", and I wasn't able to deactivate it with the other suggestions in this post.
So far, I found a slightly ridiculous but effective workaround to move around multiple files, hopefully it helps getting insight into the other issues:
- Click and drag to select the desired files
- Pressing control or shift, click once on the file you will use as pivot (and then release). This will deselect that particular file
- Still pressing control or shift, click on the pivot file and drag. All files will move around.
This way, files can also be moved into folders that are present in the desktop, but not into other opened windows.
The problem was that, if you don't do step 2, all the files except the pivot would move around. This smells like a bug to me but could be indeed a (rather experimental if you ask me) feature.
Cheers,
Andres