reftex-toc-confirm-promotion

reftex-toc-confirm-promotion is a variable defined in `reftex-vars.el'.
Its value is

2

Documentation:
Non-nil means, promotion/demotion commands first prompt for confirmation.
If nil, the command is executed immediately. If this is an integer N,
ask for confirmation only if N or more section commands are going to be
changed.

You can customize this variable.