Well, Zim recently dropped data from notes. I think I traced it down that it didn't save the currently open note I was editing, so that upon shutdown the edits were lost.
Time for a new tool then. I had been evaluating basKet, which turns out to be a nice trial to build a OneNote replacement, but is not being actively developed since 3 years !
One of the alternative tools I had found was cherrytree.
Though being a gtk application, it seems to do the job. One negative aspect is that the data is either stored in a sqlite database or in a huge XML file. To keep the ability to access data using a text editor (eg in case of recovering from disk crash), I have choosen to use the XML file.
The tool has an importer for Zim files, that's a very positive aspect. However, though the import somehow does the job, the formating of the entries is not really what's expected (headers styles, background colors etc), and varies from post to post, which is a good sign that there is an issue with the importer and some syntax constellations.
Furthermore, some syntax constructs from Zim are not supported at all by the importer :
- nested lists (more generally, all indented stuff is not treated hierarchically as should)
- checkboxes (change requested... and accepted, waiting for implementation !)
Throught the forums I was able to reach the author, which answered within a few hours (very good sign !). I have sent him some samples from Zim to debug the importer. No answer yet, but at least the author is reactive to user input !