Someone submitted a mod to the script manager to add stickman controls, but I haven't tested it yet so it's unapproved. (And it doesn't use the stickman api that my mod / Android port has). This is the only mobile QoL mod I'm aware of.

As for your suggestion, I think the ability to do this would be limited, but certain things are possible. The main restriction is that you can't actually set ctrl/shift from Lua. But, there are Lua apis for nearly everything in the game. So there are Lua apis for drawing lines and boxes, so with enough dedication, it is technically possible to write a Lua script to draw lines / boxes on Android. It would also be possible to replicate some other shortcuts, but a lot such as ctrl+c, ctrl+v, ctrl+f, would not be possible from Lua.