Maybe a mod that allows exps to be infinite built. Idk if its possible from an ui mod but if it is it would make huge eco games alot easier
In a factory build queue, you can left-click on the icon for a tank to tell the factory to make more tanks. Or right-click to reduce the number of tanks.
In an engineer's build queue, you can right-click on the icon for a structure to tell the engineer to make 1 less of that.
Would it be possible to allow you to left-click on the icon for a structure to tell the engineer to make MORE copies of the structure? This would only work for structures that get up and walk away when completed (like T3 sonar, experimentals, crab eggs)
Left-clicking on the icon for such a structure would tell the engineer to make more copies of the thing in the same place.
That's not exactly the same thing as an infinite queue, but if you queue up 100 czars on the same "footprint" with just 20 clicks that would be more efficient and not very different from being able to do an infinite queue.
Alternatively, a solution to your problem might be a SIM mod: make a new factory type called "experimental factory" that can build experimentals. For example, the factory might cost as much as 30 T3 engineers, and it would have as much build power as 30 t3 engineers and you'd need a t3 engineer to make it. That would be an easy way to allow players to queue up an infinite number of experimental units for construction for big eco games. So you wouldn't need to get into the weeds of making a UI mod.