Split lines in normal mode (opposite of Shift + J)

[fillipe-gsm]

For merging multiple lines there is the J keymap. For instance, if I have

def my_function(
    variable: int
) -> int:

if my cursor is on the first line I can press J twice and get

def my_function(variable: int) -> int:

all of this in normal mode.
But for the opposite I have to move the cursor right before variable, go to Insert mode, press the return key, go back to Normal mode, and repeat. This gets tedious really quickly on multiple formatting.

On Vim and Neovim I managed to map Ctrl + j to the <nl> command, but any other combination on normal mode should be fine.
Is it possible to do the same with Helix?

Edit: replace Shift + j with simply J.

[the-mikedavis]

What is <nl> in Vim? It inserts a newline?

Macro key-bindings would be a solution for this - you could bind a key to enter insert mode, add a newline, and go back to normal mode #1383

[fillipe-gsm]

Thanks for the quick response.
So instead of an actual macro key-binding I follow your suggestion and added a new key mapping:

# config.toml
[keys.normal]
C-j = ["insert_mode", "insert_newline", "normal_mode"]

so I can now add line breaks in specific points without leaving normal mode.

Thank you once more!