In case anyone was looking for this, here is how you apply customized groupings to check edits done for similar positions (e.g., all offensive linemen, all DB's).
*On any given team, choose a given singular position, like QB.
*At the bottom of the editor you will now see that position in the grey band with a check mark and red X in the lower left. To the lower right you see the option for "Customize..."; click that.
*You can now "Open..." and choose one of the groupings I've already made (attached; just house them somewhere on your PC), or you can make new ones.