Apologies, I should have clarified how you can use the text I quoted.
The only way to specify custom coordinates without clicking on the map is by pressing this button:
This will enter the “manual editing” mode. From here, you can specify coordinates in the format shown in the text I quoted. In your case, it would look something like this I assume:
KSCH DCT 429400N0737100W DCT KSCH
Typing that route and pressing “Done” results in the following flightplan:
Is that what you were looking for?
Kind Regards,
Malte