Comment 18 for bug 316922

I'm in favor of #12. Keep it simple and consistent. Show parents in the same way you show sub-tasks - with links inside the task editor. Use arrow in different direction "<-" instead of "->" to designate parents in combination with a different indent.
Adding buttons, panels, etc. will add unnecessary bells and whistles.

Use case: I'm planning a project to prepare a documentation packet where I have to collect a bunch of information from different people (e.g. production manager Mike). Planning goes like this:

- prepare product qualification docs for customer xxx
-- product manufacturing documentation
--- fab documentation
---- meet with Mike
----- schedule meeting with Mike
--- assembly documentation
---- meet with Mike
----- schedule meeting with Mike
--- production test documentation
---- meet with Mike
----- schedule meeting with Mike

"meet with Mike" has 3 parents. I need to be able to click on "meet with Mike" and see a list of what I need to discuss.

Same for shopping lists. According to GTG philosophy, "go to store x" should be the last sub-task after a bunch of "buy XX" tasks.

meet with Mike task should have a list of links to parents and children like this:
<- fab documentation
<- assembly documentation
<- production test documentation
   -> schedule meeting with Mike

Consistent and easy. Alternatively, "/" can be used to designate children and "\" - to designate parents. Placing the title between parents and children makes sense.

Adding a "+" to expand each item to trace the tree further would be nice too:

<-+fab documentation

would become

<-+ product manufacturing documentation
    <- fab documentation

etc.

Any tree can be inverted. If we start from a given node, it's easy to list children and children of children in one direction and, identically, parents and parents of parents in the other direction, if we do not attempt to list other parents of children.

Make sure you catch circular relationships.

I hope, I'm not too late with these ideas.