Wouldn't it be better to use just one syntax and message for what to do ON COMMIT ?
When creating a new variable you use
CREATE VARIABLE ... ON COMMIT DROP | ON TRANSACTION END RESET
On PSQL \dV+ you show
Transactional end action
Maybe all them could be just ON COMMIT
CREATE VARIABLE ... [ON COMMIT {NO ACTION, DROP, RESET}] and \dV+ just "on commit" on title column