[FEATURE] Column sorting for selected records

[roanbear]

Users are added to the selected collection based on the order in which they were selected.
This makes deselecting a user from the right column more difficult.
A workaround is to search for the user on the left column via sorting

Ideally the selected column headers would behave like the left column headers.
The deselect icon does not have to be sortable since there is no variation in the values of those records.