Download Activation Graph System Free Unity.
In the Activation Graph System, you can build up a node system for e.g. mission system, research system, build system, crafting system, and much more. It can serve also as a timeline editor. All these different kind of nodes in the graphs can be connected with each other, e.g. you can connect a mission task with a research task. I developed this graph system for my mission flow, but it is so powerful, that I already use it for my tech tree and build tree. The Activation Graph System does not generate any code in the background, it instantiates GameObjects with a specific node script, that can be configured.
Full source code available.
Open the Activation Graph System, create some tasks and conditions, connect them. Roughly, thats all.
Attention: If you update your version 1.2, then you will lost all the item values on the user conditions and containers. However, such changes shouldn’t be happen in the future releases.