It is a campaign file with a single level that gives map makers more tools for their own levels. If you are already aware of ExecuteFunction in triggers, you probably won't find anything interesting here. This template was made for people who don't want to do triggers, but still want more than what the level editor has to offer. Lazy people like me might want to use it as well.
You can download the custom level here[drive.google.com]. Then you have to place it in your Levels folder.

To edit the level settings, you have to go to the TEMPLATE_SETUP trigger, select the setting you want to activate, then put 1 or higher instead of 0.

INFINITE_AMMO : Self explanatory. You always are full of ammos.

BROS_MEGA_GUN : Bros shoots way faster but their special attacks are disabled. It can have other undesired effects.

INFINITE_STEROIDS : Self explanatory. You always are under the steroid effect.

AUTO_ROLL : Makes you roll for no reason.

PARACHUTE_START : Bros starts the level on a parachute.

You can tag doodads using the "Doodads Properties" tab. With this template, some specific tags have special effects. You can't add multiple tags to a doodad.

"buff1" : Spawns with +5HP.
"buff2" : Spawns with +10HP.
"buff3" : Spawns with +20HP.
"buff4" : Spawns with +50HP.
"buff5" : Spawns with +100HP.
"Immortal" : Can't get hit by anything.
"Dead" : Spawns dead.

"MegaDog" : The dog spawns as a big dog.
"SuperVehicle" : Shoots projectiles faster and has more health.
"MegaGun" : Mooks shoots more projectiles at a time.
"SuperGrenadier" : The grenadier throws grenades faster.
"SuicideGrenadier" : The grenadier spawns grenade at himself.
"EvilVillager" : The villager spawns as an enemy and will attack bros.
"Parachute" : The mook spawns with a Parachute. Doesn't work on scouts and bruisers.

"InfiniteFuel" : The mech has an infinite amount of fuel.
"FriendlyWallOfGuns" : The walls of guns never triggers.

"BloodyDrill" : The drill spawns with its bloody textures.
"American Mech" : The mech has an american flag instead of a skull. Still is an enemy and has a mook inside.
"DeadHead" : The worm has no head (except when shooting).
"SuperDeadHead" : The worm has no head (and cannot shoot).
"MegaBleed" : Always bleed, even when dead.
"SuspendedCorpse" : Gets suspended at the roof and dies.
"Hiccough" : The poor mook is a bit sick... :(

"RedWorm" : The worm looks red.
"RedMech" : The mech looks red.

"StuckForceField" : The forcefield doesn't expand and deals no damage.
"AutoElevator" : The elevator goes up and down with no interaction.
"SuperBoulder" : The boulder destroys every block it falls on.