There is no such command to disable only the E stepper drivers. This command M84 gets interpreted as disabling ALL stepper drivers, which on some printers would cause the print bed to fall down.
It has to iterate over all layers and do string comparison to find the index back. Instead we just keep track of the index so this should improve performance a bit.
Instead of making lots of nested if statements, use the if statements as an interruption check. This reduces the indentation a lot and makes it easier to read in my opinion. It also makes it easier to add stuff to these checks.
