Layers from dependencies
A task can stand alone and be linked later. One prerequisite is the usual case. Several are allowed, and the map rebuilds from those edges.
A to-do list, grown as a skill tree
To 
Do
Each task is a node. Prerequisites are the paths between them. The map lays itself out in layers, the way a role-playing tech tree does, and you pan, zoom, and drag links as the work changes.
Three ways to shape it
Add a single task, paste a list with prerequisites, or press the plus under a node and name the next step right on the map.
A grove for each set of trees
A grove is one complete collection of skill trees. Keep work, home, and campaigns in separate groves and switch from the header.