I have not noticed this problem. So long as you are editing the details panel of an actor/component which is placed in your level, I believe you should be able to reference other placed actors. If you can’t, I think that would be a bug.
I agree completely, this should be changed.
I don’t entirely follow you. Generally speaking, you should avoid writing blueprints which have a hard dependency on the existence of a particular instance of an actor. If you keep needing to do this, I’d say there is something wrong with your approach.
I guess the exception would be if you have a particular actor of which there will always be one instance in every level of your game - for example, an actor which acts as a manager for an in-game system you have. In that case I’d suggest adding a (public) variable somewhere which is globally accessible, in a custom Game Mode perhaps. You initialize this within InitGame/BeginPlay, then in your other blueprints you can call GetGameMode, cast it to your custom mode, and access the actor through the variable.