Two ways that the behaviors differ from built-in parameters (probably related):

• Cannot manually set a parameter as one of the added parameters (they only appear when checking the box)

• When deploying a train schedule without setting the parameter, instead of the parameter it becomes whatever item/signal the parameter originally substituted (e.g. if you created the blueprint by substituting iron plates for parameter A, it puts iron plates on the schedule)

I'm guessing they just need to be added to the list of signals?

Correction: The parameters don't work correctly in train schedules whether or not the parameter is set. So if you create the blueprint with the parameter substituting iron plates, then place the blueprint using the parameter as inserters... the train schedule still uses iron plates.

whoops. accidental double post