Layers sure can be helpful for stuff like this.
I make it simple though because I can confuse myself way too often.
I made a layer caller locked layer in my routes
Whenever I want to place things on platforms or loading docks, I lock the station or loading dock asset , by switching them to the locked layer then move my accessories into place. When that's done, I then make sure I switch the station or platform back most of the time.
The reason why I lock just the platform or station is I then do have to remember to unlock or merge multiple objects, and only have to deal with a single one.
John