How do I add fluid tags to fluids from external mods?

Put simply, I want to add a fluid from another mod to a tag from another mod. An example would be adding oil from Thermal to the create:bottomless/allow fluid tag. What I'm asking, is how I would do this, particularly for Forge 1.20.1 and MCreator 2024.4. If I have to use custom elements, give me some code that I can easily alter for any tag and any fluid(s), that's all I'm asking for help with. Thanks.