I’ve found a problem with grouped stations.
I started a new rail line from a station that’s grouped with a bus stop, the game assumed that it is bus line, not a rail line although I selected the ‘rail line’ tab before starting the line. This resulted in a dysfunctional line that you cannot assign trains to.
It looks like you need to un-group a station before assigning to new line. This should not be necessary!
This leads me to ask a question; what’s the advantage of grouping stations apart from the convenience of a single name?