I checked Radix which is where these components come from and it appears its not supported right now but a requested feature
https://github.com/radix-ui/primitives/issues/1270here's a workaround found in one of those comments:
just FYI, you can implement multiselect with the dropdown component and checkbox items
it is a strange way to do it, but should be pretty easy to implement
However, we are working on adding a native select list (not radix) and I dont see why this wouldnt be supported @Ivan Starkov correct me if I'm wrong