I'm not sure about ALL of Europe, but I know that some countries require separate amber turn signals on the rear of the vehicle. The American standard when Excursions were built is to use the same red lens on the rear for turn signal and brake light , same bulb 2 filaments.
I have no idea what the German lighting requirements are for a trailer, but if it is similar requirement to have separate brake & turn lenses then the circuits may be able to be joined and outputted from the rear vehicle lights to the lights for the trailer.

The American spec Excursion uses a separate circuit for the trailer lights, separate from the vehicle lights, and also a special dedicated circuit for the trailer brake control. I strongly recommend that you do not modify the trailer brake control circuit for safety reasons.

If your Excursion has already been modified with rear amber turn signals, then it may be a simple matter to tap into the vehicle light circuit, depending on the vehicle wiring standards for your country and/or any other EU countries you may drive through.

Has the Excursion been modified to use the amber turn signals?
If not, there is a tutorial on how to do that here:
https://www.ford-trucks.com/forums/1...llow-turn.html

It would help to know your Excursion's current status, and exactly what has already been done to modify the lighting,
and exactly which trailer connector it has,
and exactly which connector is on the trailer you plan to tow.

Great info from Sam. I converted mine to have amber turn signals in the back, but that conversion messed with the trailer wiring.

I don't know what's required in Germany for trailer lights...but the trailer feed from the Excursion may or may not supply what is needed. Perhaps that adapter that I mention in the link above may help.