I often have "muster points" for units, meaning I will move all nearby idle units onto the same tile and "Sentry" them until required. These muster points may contain many dozens of units.
Currently I usually move all my units first, then return to the muster points. Typically from a muster point I will need 8 engineers loaded onto a transport, 12 sent to flatten a mountain, and so forth. Therefore I "ready" all the engineers on one of those tiles; slide one sideways and sentry it then repeat until I have the required number; sentry the remaining units at the muster point; ready the new pile; select all units (which is now the required number); then finally I can move them en masse.
What would be "nice to have" would be a selection box within the dialog where I could specify the required number of units, then I could simply open the unit selection dialog and for example select just the 8 to move to the coastal city for transportation
