It's not currently possible to multi-select in the navigation tree for some reason.

This is the first thing the user will try - before realizing its not possible and they have to start to create tons of views (even for the simplest filtration..).

This is a MANDATORY feature of any task software. Think about it :)

Let's say I would like to display all my tasks with the context of @errands - but only those who belongs to my "Private" project... what do I do? Yes. I try to select first @errands, then I try long-pressing it, hoping to get a selection check-box next to it, so that I can check it along with my "Private" project..

Then a moment of frustration.
Then I have to create a new view to accomplish this simple task.
This way I end up with Too Many Views.

My spontaneous (but not necessarily the best) suggestion for implementation is to enable a check-box pane to the right in the pane list view when long pressing any item. The back-button would cancel out of this mode.
In the "checkbox-mode" the pane also displays a "clear all checkboxes" button either on the top or bottom of the list view (always visible).

A simpler implementation might be to skip the check-boxes and just enable multi-select mode after a long-press which is canceled by stepping back.. but I am not sure that is as clear to the user.

What do you think?