Since you override some variables i guess you are using a NeoLoad project right? But then what do you want to override? There's a difference between creating a variable in the yaml file and override them.

As you stated inside the yaml file you can only create 4 different variable types. If your goal is to use a random UUID variable you can create that variable in your project and use it if needed in your yaml file.

But if your goal is to only use a yaml file (without any NeoLoad project created beforehand) maybe you could add a Javascript action in your yaml (available since 6.10) and use a function to generate that random UUID. You can find such function if you google it.