Follow up:

I've been working with TreeLine on the N800 for a day now. Although the main screen lays out just fine, there are several dialogs that are unusable because they simply contain more controls than can fit on the N800 screen, so the controls and texts are jumbled on top of each other.

Also, it is optimized for keyboard use -- it has dozens of keyboard shortcuts that otherwise require a whole lot of nested menu navigation.

So my preliminary assessment is that TreeLine and the N800 are not a very good fit. That's a shame, because I can see by using it on my Kubuntu desktop computer that it has just about exactly the functionality that I want.

I will have to decide if the functionality is so critical to me, that I will take the time to re-work it to make it more suitable for the N800.

(Also, it takes about ten seconds to start.)