Depends what you mean by 'freehand'.
There is a 'remarks' box on the FDE, on ours it appears to the right of the callsign/type/squawk box, on the upper half of the FDE.
You can enter whatever you like here, and it colours the box yellow. You enter text via the qwerty keyboard popup; we added quite a few shortcut buttons, such as '1 ENG', 'MEDICAL', 'PAN', 'LTMA' etc etc, so I guess you'll have similar.
I do not envy you guys having to cope with freecallers!!!!! We've managed to limit our 'freecallers' by making airlines 'book out' their towing movements with Apron who enter it into EFPS so we should have a strip waiting for us when the tug crew call.