Request: next/previous movement keys for subheadings

[elig0n]

i would like to suggest to implement a forward/backward item keys for a level. For example via Ctrl-j and Ctrl-k which will move between plainlist and all other types of subheadings that share the same indented level, in a manner similar to NerdTree.
]] and [[ should probably stay for top level navigation.

Rational: most of the lengthy content stays in subheadings rather than top level headings which are most often used for headers and often a 'j' or 'k' button will do, than ]] and [[.