What is the way to include the fact that gas injection is f.ex 95% of produced gas? I have both gas production potential profiles for the producers and gas injection potential profile for a gas injector included in my setup.

Currently we do not have a function in pForecast for directly defining injection as a percentage of production.

However, you could use a voidage group where you would define PVT properties to limit the injection according to gas production. This voidage group would contain both the injector(s) and producer(s).