Actually completed and released long ago

Yeah, the design process is like that - full of compromises ;)

Time and Link tabs would offer access to quick filtering notes by date/time (instead of the current nearly defunct search by date) and by the Link (will present the alphabetically sorted list of 1st level domains).

Seems indeed to be the best solution overall. But please also comment on the "another idea" from below, about adding mini-tabs to the sidebar.

Well you could:
1) Make CN's window wider
2) Decrease the sectionbar.tab.width.min parameter

Thank you Stuart for this comment! I agree that using the right side for tabs is not the best idea. Probably the best solution would be to provide 2 sets of tabs for notebooks and sections, where the user can pick the position of each. 

Also here's another idea:
- make sidebar full-height, and add tabs to it: "Notebooks", "Tags", "Time", "Link" (using icons instead of text to keep it narrow)
- list all open notebooks on the Notebooks tab
- keep section tabs on top of notes list.

I agree that this is practical, but I think we can do better. Probably if we make the sidebar full-height, it'll provide a better visual cue. Actually even 2 rows of tabs with configurable positions looks better to me)