I had no idea, thank you for sharing!
I have a different issue than yours, I can find the Group Sorting section but the interface works strange compared to what I expect. When selecting the main output node; I get one Parameter Group per parameter and not per group.
I have 4 parameters, and it shows 4 indexes in the Group Sorting:
However, it still works somewhat:
I am using 5.0.3.
Edit:
After further testing thought that the current flow would allow me to create multiple groups of the same name in various orders, but that doesn’t work.
The I think the indexes play some role in the of the placement of groups. In this case:
Index 1 seem to take priority over Index 2:
I really don’t know what is going on… 