This is a copy-paste of the steam page

Cheats & Useful Tricks (Like skipping the first caves)
Here's a list of cheats, tricks and console commands if you want to have some fun.
You can find a full list here[zdoom.org], but I've also extracted some of the more useful ones below.
Please report any broken links!


Useful Tricks
1. Skip cave part in first level:
https://postimg.cc/mPhLmwd6

2. Beta hub with level select (also see the Changemap commands below):
https://postimg.cc/pmkjFqmG

3. Skip "cinematic" segment of Map06 (v1.3.2 and up):
https://postimg.cc/QBDnf7kf


Cheats
To activate cheats, open the console (with ~) and type the following
(FYI GZDoom's console supports scrolling and ctrl+c ctrl+v):

General Cheats
god - makes you immune to damage and gives Zan glowy eyes
noclip - you can clip through vertical surfaces
fly - allows you to fly
notarget - monsters will not attack you unless provoked
resurrect - restores you to back to life with 100hp when dead
give all - gives 200 armor, backpack upgrade, all weapons and ammo and all inventory items that can be carried in more than one (including Quest Items)
give weapons - gives all the weapons, without any reserve ammo
give key - where key is: IronKey, StoneKey, VineKey, AxeKey, EarthKey, CrystalKey
give ammo - gives full reserve ammo (without backpack upgrade)
give InventoryBagOfHolding - gives backpack upgrade (only the first time) and two ammo magazines for each weapon
give health X - gives X hp (works to infinite amounts although the HUD counter caps at 999)
give armor - sets your armor value to 200 (on lowest armor quality)
give LightArmorCrystal / MediumArmorCrystal / HeavyArmorCrystal - gives the respective armors
kill monsters - kills every monster in the level (warning, it also kills important monsters that are needed for some progress scripts, use the remove actor detailed below instead)
anubis - gives you fear aura similar to the Choker of the Beast's effect

Remember that you can also replace give with take to have the opposite effect.
WARNING: If you use the take all command, make sure to follow up with give IsPlayer and give IsPlaying or some scripts will mess up.

Consumables:
give consumable X - where X is the quantity (leave blank if you only want 1x) and consumable is one of the following:
InventoryTimeShard
InventoryFixerGoggles
InventoryVialOfHealing
InventoryPotionOfStoneskin
InventoryPotionOfHaste
InventoryPotionOfMight
InventoryAmuletOfShadows
InventoryElementalRing
InventoryChokerOfTheBeast
InventorySentryGun
InventoryScrollAirWizardsEye
InventoryMysteryPotion

Weapons:
give weapon - where weapon is one of the following:
Fists (you have them by default but you can lose them via the take command)
Axe
SpikeGun
SpikeMag (ammo)
FragfireGun
FragfireCan (ammo)
Crushbow
Boltmag (ammo)
PotionLauncher (gives both toxic and acid launchers)
PotionLauncherAcid
PotionBoxAcid (ammo)
PotionLauncherToxic
PotionBoxToxic (ammo)
Crylance
PowerShard (ammo and +3 armor)
DepletedShard X (just ammo, X is value)
Hellclaw
HellEnergy X
HatchetAndShield
FireHammer
ForcePike
GreatAxe

Summons
You can summon any actor in the game using the summon actor command, where actor is the name inside the DECORATE file. Alternatively, you can use remove actor to remove ALL the actors of that type from the level. For monsters, you can replace summon with summonfriend which will turn them friendly upon spawn. Here are some of the more useful names for actor:

Friendlies:
IDSentry
IDBearWarrior
IDReaver
IDLancer

Enemies (using remove will remove all the enemies of the specified type from the map):
Hellblaze
Crawler
Conscript
Cultist
SniperCultist
Initiate
Cerberus
IronUrchin
ForgeElemental
IronMaiden
ShieldWallIronMaiden
Warlock
Golem
PitLord

Bosses:
GiantNithriel
PitLordAlpha

Critters:
CritterCandlefly
CritterGhostEel
CritterPraak

Level/Music Change
changemap map - changes the level, where map is: Map01, Map02, Map03 etc.
nextmap - moves you to the next map and also resets your health and inventory
Note: If you use cheats to move to a map that requires items such as the Pickaxe from a previous level, these items will be spawned in the level, and you only need to find them to be able to progress normally.

changemus track - changes the music, where track is: HTrack01, HTrack02, HTrack03 etc.

Other Useful Console Commands
vid_fps 1 - shows fps, type again with value 0 to toggle off
vid_maxfps 60 - caps fps to 60, useful to avoid fps spikes that feel like short lags
fov X - changes field of view to X value (default is 90)
bind X "Y" - binds a key X to a command Y (for example "quicksave" or "quickload")
For more debug commands check the full list here[zdoom.org].