Bled my rear brake last night, as a result it seems as sharp as ever but the lever return is noticeably slower than before (and slower than the front brake)
Could it be my poor bleeding performance has retained some air in the upper/master cylinder area?
FTR, I am able to squeeze the rear lever closer to the bar than the front.

ZipTie the lever to the bar overnight/couple of hours. Then remove the ziptie fit the bucket or syringe to the lever, then either top down or caliper bleed. Maybe some bubbles will come out.

Or try lubing your lever pivots etc. Could just be some muck on the pivots. I had my dropper post lever touching the pivot once and that was causing a slow lever return.

the back brake 785 levers seem to do this, I found a replacement lever was the only way to fix it – original lasted 3 yrs though.

Ironically it was functioning perfectly before I bled it – I just needed a slightly longer brake line.