The short answer is no. Modding is not supported in Ultimate Chicken Horse.

The longer answer is that you might find some people on the Internet sharing "mods" for the game, and these might be anywhere on the spectrum from innocuous to intentionally malicious. None of them are approved by us.

One kind of artisanal modding you might encounter offers alternate skins for characters. We do not see the harm in individuals experimenting with this, but we still do not encourage the use of such modding tools for the following reasons:

• Clever Endeavour does not offer support for game mods, modding tools, or game errors that result from the use of mods. We can take no responsibility for restoring your save files or game progress if they are somehow damaged by modding.
• We also do not endorse any of the tools that exist for modding or unpacking compiled Unity games. They are executables from untrusted sources, so there's always a risk that they could contain malicious software or otherwise cause damage to your computer.
• As per our End-User License Agreement (EULA), you are not allowed to make and distribute a copy of the game or of any of its files. This means that any modding has to happen without sharing game files between users; otherwise, it's piracy!
• While we see no real issue with local cosmetic mods, we remind you that altering your game files in a way that would modify the online gameplay experience in any way is considered to be hacking or cheating. That is absolutely not permitted and could result in a permanent IP ban from the game! Be careful, because you might not always realize what is networked and what isn't.

We have also heard tales of mods specifically designed to give the user an advantage in online games, or to give them means to be otherwise disruptive. As stated above, these kinds of mods constitute hacking and cheating, and can get you banned from the game entirely. In addition, you should always be very careful with such clandestine software, as it can easily be used to introduce Trojan horses and spyware to your machine.