Feature request - nesting arrows according to call nesting

[marekdef]

Thanks for the neat project,
I managed to run this plugin in a project (kotlin + java) without major issues.
If a function1 calls function2 we would see sth like
-> function1
-> function2
<- function2
<- function1

would it be possible to add level of nesting so is easier to figure out call hierarchy?
sth like
-> function1
--> function2
<- function2 (not sure really if it should have two hyphens or one and a space)
<- function1

or similar with spaces indicating nesting level?