My suggestion is to have a regroup party (regroup all) button in the button left next to character portraits that does just that - for characters "in range", of course. After battles where you wanted to position characters specifically, it would make things so much more convenient than manually reattaching them to each other after.
---
Also a possible bug with character portraits..?
I'm having a frequent issue when I click character portraits that it doesn't select them on my first click, unless, I very intentionally click their portrait while generally centered on it. Not sure if I'm just too quick, but it doesn't seem quite right.
Thanks for reading! Great game so far!