Trying it just now, found what's probably the biggest cause of confusion - which layer are you editing. Edit route button does the route layer, doesn't do anything with the session layer as long as you don't select the trains tab. Edit session and you're starting in the session layer by default. So I select the master session, the empty one with the same name as the route, edit session. Reason I'm going in there is to add some directional track markers to stop the idiots from getting into standoffs, if there's a way to choose the wrong track anywhere they'll find it even if you have their path festooned with 63 navigate via markers. So I added a bunch of directional markers to the center track, change it from bidirectional to one way, save, leave it at the default overwrite route and overwrite session. Before running I edited the test session to check, sure enough all them new directional markers are gone. :'( Back into the master session, there they are!
Check the layers, I'm in the session layer. Okay, let's try this; merge layers, merge the session layer into the route layer. Save, exit, back to the other session and edit, all directional markers present and accounted for SIR! :wave: Since they're in the route layer now they're in every session.
As for the switches, that's more due to the tracklaying tool trying to "help" than anything else, place two carefully straightened parallel tracks, make a crossover, "here, let me help by bending all the connected tracks into improbable shapes". Straighten all that out and add a second crossover going the other way, "oh let me move the switch lever for you over to this new switch". Now the new switch has two levers and the old one has no levers, I suspect however you edit the route you'll always need to watch out for that bit of lunacy.

As for the switches, that's more due to the tracklaying tool trying to "help" than anything else, place two carefully straightened parallel tracks, make a crossover, "here, let me help by bending all the connected tracks into improbable shapes". Straighten all that out and add a second crossover going the other way, "oh let me move the switch lever for you over to this new switch". Now the new switch has two levers and the old one has no levers, I suspect however you edit the route you'll always need to watch out for that bit of lunacy.