I usually use [area interface where basemulti
...and manually set the Location or X/Y/Z, or use the interface to move the multi.
You could also edit the [props command, to detect if a multi exists at the target, and opens the props gump for it as well as the target.
The reason [Move isn't supported is because multis are technically one item, so targeting the corner of a multi would actually select the 'center' tile and move that, which could provide unexpected results where the user expects the targeted piece to move to the targeted tile.
In order to make it work properly, you'd need to do a bit of math o offset the source and destination targets, versus the multi's center tile offset and location in the world.