Is there a way to freeze/lock/fix a sortable item in place by index while maintaining the normal sorting behavior?

[MorkWood2]

I'd like to create a reorder.group with many sortable reorder items and I was wondering the possibility for setting a specific item to be fixed so that it maintains it's index and other cards are moved around the fixed item as though it is a nominal behavior. Haven't seen an example of it, nor anything in the docs that can pull off that magic.