You can work around that in fusion and onshape by creating a parameter master “part” from which you derive your other parts. It works but is clunky. Onshape has the ability to make a variable externally visible to the assembly which includes the part which is cool for rails and shafts because you can set their dimensions when importing them, could not find that in fusion.
Primarily my private instance, but if you like the URL create an account. This instance is targeted at makers and software developers.