dialog message :
Rename Failed
Could not rename “New Group” to “cardSelection”.
Rename a new created group in project navigation pane failed
Which XCode version ?
I just tested renaming a group that had files inside.
Created a new group and changed the name immediately.
In each case, no problem on XCode 10.2.1
xcode version 10.2.1 on macOs mojave 10.14.4
Restarting xcode solves the problem every time it occurs.
So can you describe a complete case where it occurs ?
select Group then press Enter key to rename in XCode