Task scheduling tool (forked)?

Question

linux

I am looking for a convenient tool for organizing my “it needs to be done” with the possibility of branching tasks, creating “trees” like doing one task - then 3 more branch off from it. For example, buy an ax - (build a house + make peace with a neighbor). And it is desirable that, for example, all these things go horizontally with reference to the time scale. As in any games like the era of empires, "research" is going on.
Prompt such service or application. Better service.
Linux Mint.

Answer 1

http://www.xmind.net/ or any other mind-map "editor".