outline-demote
outline-demote is an interactive compiled Lisp function in `outline.el
'.
(outline-demote &optional WHICH)
Demote headings lower down the tree.
If transient-mark-mode is on, and mark is active, demote headings in
the region (from a Lisp program, pass `region' for WHICH). Otherwise:
without prefix argument, demote current heading and all headings in the
subtree (from a Lisp program, pass `subtree' for WHICH); with prefix
argument, demote just the current heading (from a Lisp program, pass
nil for WHICH, or do not pass any argument).