It would be nice if the ATC map displayed a fixed minimum size hold oval for all holds. I say minimum size oval because pilot holds are sized based on speed. That’s not necessary on the ATC map, so a fixed size oval will work fine. We just want to know if pilots are reasonably close to the hold.
Adding someone to an existing hold would be accomplished as follows. Click and hold on the aircraft you want to add and drag them to anywhere inside an existing hold. When you release the drag, select hold and they will be given the heading to fly to the south turn entry and the hold oval will be displayed there.
Finally, clicking on any aircraft in the hold would bring up a drop down list of selectable aircraft currently in the hold, sorted by altitude. This will facilitate dropping aircraft altitudes in the hold.