In a reference selector, you can set the select-using property to form, and then in the form achieve the desired behavior.
In addition to my previous answer, you can use the onchange microflow as well, which returns the new set of microflows to be displayed.
I ran in to this problem myself some time ago. A feature request is up for it in the Partner Portal, under nr. 4663.
Don't know when we can get an easy solution for this though, until then you're best off using Michel's great suggestion.