When i place a train with the trainbuilder there is no fuel in the train and it can't drive out automatically, because of custom fuel. And unfortunately you can't put the fuel in the train with a inserter (modded, 3 fields wide) because the train doesn't pick it up as long as the train is in the trainbuilder....
Can you pls fix one of this problems?
Mod: Yuoki Industries - Railways and addons from Yuoki

I'm having the same problem with the mod "SE Space Trains" by FragJacker.

You could try editing the mod like this https://github.com/voske123/FactorioMod-trainConstructionSite/pull/96/commits/ee5d648e850b6468218e251252341b9d957588e6 and submitting a pull request

2 years later and this solution worked for me.

A lot like adding a new fuel type for the Jetpack mod.