php flarum migrate
Flarum does not have the same migration rollback as Laravel though, so you cannot roll back step by step. The only way to revert a migration is with the
php flarum migrate:reset --extension= command which will run the down method for all migrations of the given extension. This can fail if you did not first reset the other extensions that depend on the extension you are developing.
You can always manually delete the migration entry and changed in the database to try running the same migration again with the first command.