Effect counters are worked. It's very late, because it only worked on Flatpak build and on my host system was some errors. I removed error and game worked on my host system, so I updated source code.
Progress1 ruleset already use counters to provide golden age mechanism. Each turn you have palace built (so your people are happy), one counter increases. When it is bigger than some other counter, golden age start. Additionally, points required for next golden age increases on each golden age acquired.
Also, I implemented custom_multiplier. Custom_multiplier is multiplier from req list, so it can be any integer value we can access from req list. In future I will add more values, but at now you can access only counters.
I will now implement civic lock, so game could behaves like CivV - when selecting civic, you cannot change it and you can select new civic once you acquired some culture points.
I still waiting for your suggestions and help.