PaladinNO: I don't know how to mod WITH GoG Galaxy... 
 I have only installed offline mods, without RedMod.  
 Download CyberEngineTweaks and any other required mod frameworks from NexusMods and go ham with whatever mods you want. :)  
https://www.nexusmods.com/cyberpunk2077/mods/107   Mods are installed adding files to the install directory, usually to the bin and r6 folders.  
 Is there any mod or feature in particular you are looking for? 
 I can recommend Let There Be Flight.  
https://www.nexusmods.com/cyberpunk2077/mods/5208?tab=description   Has a ton of framework requirements: 
 Input Loader 
 Mod Settings 
 RED4ext 
 redscript 
 TweakXL  
 ...but it works great!  
 I am playing on patch 1.6, as there has been too many reported issues with 1.61. 
  Thanks for the ideas! I'm sorry, I should have mentioned, but it's installed on a Steamdeck. Anyway I installed Cyber Engine Tweaks. According to what I found online, a notice should pop up to configure some hot keys, but nothing happens. Also, i wanted to use RedMod because I made some changes to some files called "tweaks" on my main pc, and I wanted to use them on my Deck as well.