There is no way in Baldur's Gate3 to command multiple characters at once.
Isnt that by design?
I mean people were complaining a lot about ability to start fight with single character ... and then sneak by with another one and attack ... then sneak by with another one and attack ... and then sneak by with another one and attack ... (and it doesnt end here if you are moding

)
Dont get mad, but i dont see much difference in the end between this "ugly and hated gimmick" and that "beautifull and purposefull, and who knows what else full function". :-/
I can understand why would you concider such function to be one of the most essential things engine HAVE to do in any real-time game ...
But in turn based? Im not really sure what do you need that for man. :-/
Chain system:
Use ungroup all. Drag portraits around and hope the chain will stick. Pick one in the group and tell them where to go. Group the other two and do the same. Doing just that will likely take more time then all of the above. Want to do anything more specific - either take them all one by one, or you need to wait until the first order is complete (doing anything will cancel whatever order was given) when seperate the two and then give a new order to the one you want to move. Esencially chaining is an extra step you have to do, that you don't have to do in the old system. And of course, in all that you pray that AI won't get confused, the folower won't go through the vision cone, or trap or hazard and force a reload. That can get improved with AI, but again it's all unnecessary complication, that wouldn't be needed if players had precise control over character's movement.
That is certainly one of options ...
OR you can force turn-based ... and send them one-by-one to their locations ...
OR you can press ungroup ... and send them one-by-one to their locations ...
I mean yeah you described the least effective way to move your party, but that doesnt mean its the only way. :-/
I dont quite see the reason for chaining them ... especialy if (concidering your own description) have problems with that (aka.: "hope the chain will stick")
In my opinion Backspace (ungroup) ... F1 > move mouse to position > Click ... F2 > move mouse to position > Click ... F3 > move mouse to position > Click ... F4 > move mouse to position > Click ... and voila.
I often set ambushes like this ... and it rarely takes me more than few seconds. :-/
(and yes sometimes i metagame when i do ... but some i set it even for first atempt back in Patch 1, so i dont count those ... for example Githyanki Patrol ... gosh i cant imagine how could Larian make them seem more dangerous and warn us, than post there huge neon sign saying "hard encounter, saving recomended!"

)
I agree on traps and cones tho ...
But i dont think it is anyhow linked to chaining or not-chaining ... that is more like NPC AI movement problem ... and it would be just as shitty as if we were Shift-Clicking our microparty members.

And you might say: well, that's real-time game, it's different. And yes you are right...
I totally was going to.

Cant imagine doing something like that in turn based in first place.
