Via #3091 it seems like a sensible option to allow users to update the costmap only on a request (e.g. planning or control). This comes with downsides I outline in my response in #3091 but there are definitely situations where that would be a sensible choice.

This should be really easy as the user outlines in #3091 + adding a parameter to toggle (or if the update rate is set to 0.0?).

@cf-zhang would that be something you'd be open to contributing? That + the suggestions in the other ticket would put you back in line with Nav2 source and you wouldn't have to maintain a fork.