Last but not least, stops / platforms *always* go before ways.  And for *every* stop / platform pair, the stop comes before the platform.

I know you might want to do ways first because it's hard to add stuff to a relation once the said relation is out of your view, but it's possible.

The trick is, select the element you want to add to the relation first, and then drag or move the map to whatever you have already added the relation.  *Then* do the add relation operation.