Layer 2 Custom BG and BG_Data?

[Jiffy]

I've been wondering recently, is it possible to create a room with a Custom Layer 2 BG and BG_Data? Thanks for anyone who tells me! :D

[Alisa Orlova]

Looks like you're the first person who thought about it for 20 years.

[Quietus]

If you mean editing the existing backgrounds, yes.  It's under Tools > Background editor.  If you mean can you have an editable layer 2 while also using BGData - not really.  You can sort of achieve this by having the layer 3 (water, lava, etc.) appearing behind the other layers, but it might not give you much freedom.