Based on my mail to the mailing list/group: https://groups.google.com/forum/?fromgroups=#!topic/tracksapp/eIeIj3lWBCk

For me it seems to be a very usual thing to add a new action because this new action actually needs to be done before another already existing action. As an example, I might have the action "conceive a child" and after a while I come to the conclusion that this action depends on a new (to be created) action "find a woman". Currently it seems to be impossible to "spawn" new actions based on existing ones. However, it is possible to create new actions that depend on existing actions very easily.

I just saw that my "actions" are not really actionable in the sense that some prerequisites are missing and I should have thought about the whole process earlier. I might be approaching this from the wrong direction. However, I think that not everything you note using GTD is supposed to be worked out like that - I even think that adding intermediate steps is very common.