Thanks to brianogilvie for the thread pointers. I read all three (though skimming over some areas) and if I am not mistaken the whole discussion was always mainly about whether single tasks should be forced into a "project" or simply not appear at all in the projects view. I must support donbkatz here because his two requests are exactly the two things I would like to see improved in OmniFocus and they seem not to be discussed in this form in the linked threads.
I also consider folders as larger (higher-altitute in GTD speak) goals and there are projects and single actions that need to be done to accomplish these goals. I am forced to create singleton buckets in every folder that clutter up my project tree. And I wouldn't want to see all the single actions as nodes in the sidebar tree (as depicted somewhere in the threads brianogilvie linked) - rather I would consider the folders to combine the functionality of the current folders and the currently implemented singleton buckets (i.e. folders should be "Single Actions" lists with sub-projects). Then the project list is still nicely clean and clicking on the folder lists both single actions and projects in the main pane. There is another very useful application already pointed out in the earlier threads: If you only have one singleton bucket in your library you can't focus on a particular area of your life - you can focus on the folders "Hobbies" or "Work", but you cannot discriminate between the singletons associated with hobbies or work in a central singleton bucket. The solution is to add singleton buckets to each of the folders - but then, as stated above, I think this should be a functionality of the folders that I don't have to add manually to each of the folders.
I also feel to agree with donbkatz regarding the hierarchical projects. For example, I am currently working on getting my diploma (that's the German equivalent of the Masters degree). For sure, this is a thing that will be done sometime - so it should be a project rather than a folder. Then this project holds general organizational tasks I have to do (like schedule oral examinations, get some paper work done, etc.). But I also have to write a diploma thesis which is a huge project by itself. It does not seem appropiate to have the thesis as "just" an action group inside the "Diploma" project.
To illustrate both points with a real-life example from OmniFocus:
This is an excerpt of my current library ([F] Folder, [S] Single Actions, [P] Project):
[F] Career <- This is the overarching life area
-> [S] Misc <- Singletons regarding career issues
-> [P] Diploma <- organizational diploma stuff
-> [P] Diploma Thesis <- general stuff on thesis
-> [P] Thesis: First draft <- Outline of thesis (each action corresponds to a section to write)
-> [P-onhold] Thesis: First revision <- sending thesis to friends, process comments etc.
-> [F] Chicago <- Next step in my career: PhD in Chicago
-- -> [S] Misc <- General things to prepare for getting to Chicago
-> [F] Institute <- Current step in my career: the institute I am working at
-- -> [S] Misc <- General stuff to do for/in my working group
-- -> [P] DPG Meeting <- Some conference my working group is attending
This is how I think the library should look like:
[F] Career <- also contains singletons
-> [P] Diploma
-- -> [P] Diploma Thesis
-- -- -> [P] Thesis: First draft
-- -- -> [P] Thesis: First revision <- on-hold not necessary, because "Diploma Thesis" would be sequential
-> [F] Chicago <- contains singletons
-> [F] Institute <- contains singletons
-- -> [P] DPG Meeting
I hope the point is clear.
I think the above implementation would be more elegant: At the moment, OmniFocus provides folders that can hold folders and projects, projects that hold actions, and singleton buckets that hold actions that are all next actions. With the new approach, folders and singleton buckets are merged into one type, leaving us with two instead of three atomic structural units: Folders and projects that each can hold projects and actions. The only difference is that folders can also hold folders and that all actions in folders are next actions. For those who don't appreciate this approach, will still be happy by not putting single actions into folders and having a single folder labeled "Misc" or "Single Actions" at the top of the library. So, the proposed implementation is backwards compatible and providing some powerful new structuring possibilities.
All that said, I am new both to OmniFocus and GTD, so I am happy to get any critical feedback - maybe I am just too fanatic about structure and should organize things differently?