This read only field is set when the dialog is used for selecting a schedule for a train, and it is used to filter the schedules starting with this block.
By checking this all schedules are shown without filtering on the start block.
In the example only reverse1 starts in block b0.
Only the first location is used as filter if the block is member of more locations then one.
Copy the selected Route and add it to the list with the same ID suffixed with ”(copy)”.