First check if there are any app updates.

To add a train manually, do a search in the planner, scroll down and then tap on "Add it manually”. If your station is not in the app, then link to add it manually will appear if no station can be found.

Sorry I cannot see "add it manually"

The stations exist, but the times are wrong 

Sorry yes it has worked thanks so. Much 

Scroll to the bottom of the results of the planner.

In der deutschen Version heißt es "Füge sie manuell hinzu”.

Just come across this same problem with the Caledonian Sleeper - I’ve put in a query to support but for now the manual journey entry seems to have done the job. It would be great if someone who’s done the trip from Scotland to Paris could confirm that it actually works. Thanks for the help @rvdborgt , much appreciated.