I would like to have an “archive” command that takes all completed tasks and automatically moves them to a “completed” section at the bottom of the document. So, for instance,
Would become
I like this. I don’t want completed items taking up precious screen space. I’d prefer to keep them for archival purposes. But I’m forced to delete them because there is no solution.
I’d need something more elegant than a completed section at the bottom of the doc. That would make a jumble of too many disparate items from many different lists. My design solution would be similar to an HTML anchor (or more traditional bookmark). Each node would have two properties - 1. Anchor and 2. Completed Archive.
The Anchor is a name assigned to a node (B in this example) that would be used for archives (and other related functions) that says if the name is specified and activated in node A, then continue processing here in node B.
The Completed Archive has a pulldown list can be activated to display a list of defined Anchors from which one can be selected. When a node child is marked Complete, Dynalist checks the Completed Archive value of its parent, node A in my example. If there is a value, such as the name associated with node B, the completed node is moved to the top of the list under node B.
How about hide them in settings? You can even toggle this on a per-document basis. Just so it won’t take up precious screen space.
That’s the biggest issue, I’m afraid. From what I’ve learned so far, people want to archive things, but each person wants to archive it in a specific way. 
Ideally Dynalist is all about flexibility, so it can be useful to the largest amount of people instead of a subgroup with certain habits. Unfortunately we haven’t found the flexible solution for archiving yet, mostly because the hierarchical structure. It would be much straightforward to implement this in something linear like Things.
Just a thought, but how about implementing it exactly like you have the choose inbox feature. Then people can choose where to archive.
Don’t know if this helps, but I emulate this by mirroring all documents into an “archive” directory. When I want to archive stuff, I use “Move to”.
But an automatic way to do this would be indeed awesome, especially to avoid manually doing the mirroring and requiring opt in to search in it.
I really like the approach from TaskPaper, which adds the tag “@done” and moves the item to the archive outline…
This works brilliantly in DynaList. Click on the @done tag. Select All from the filter. Move To… Pick your archive.
Brilliant!