As far as I can tell,
window_set_cursor(cr_none); native_cursor_reset();
should work because the extension will ask GM to update the cursor.
This hides it correctly, but if you then call native_cursor_set and native_cursor_update, the cursor will remain invisible until you move the mouse
native_cursor_set
native_cursor_update
Set it to any other native cursor and back immediately - there is currently a bug with detecting whether there’s a need to change the cursor.
Thanks! This solved the issue :)