Bit of an odd one here, just keen to understand if it’s just me or a more generic issue.
For all other apps, I can drag the icon from the dock to place into stage manager left, centre or right.
However when I try to do the same with Safari (and only Safari), it just doesn’t work at all.
I can repeat this 100%, has been an issue with 26.0, 26.1 and now 26.2. Can confirm this isn’t a problem on my 11” M4 iPad pro running same O/S.
Here is a video showing the issue (YouTube)
https://youtu.be/0WBGBZVHsfs