the setting is renamed to maxsectiondepth and also if it is set to 3, for example, user can only create 3 levels of subsections (in Ruslan's patch there were 1 top-level and 3 below, which made it 4 in total)
I removed the setting on the course level, it seems like overkill for me
the setting is also respected when moving the sections
This PR is based on the commit Ruslan had in https://github.com/marinaglancy/moodle-format_flexsections/pull/28 with the following changes: