I think I broke it
I had created a template list and had duplicated it and renamed it.
Then I (unintentionally!) crashed sChecklist by resizing the list column after having resized the window.
When I restarted, the last created list was not shown, so I tried to recreate it - but wasnt allowed use the same name.
It is there in the Checklist folder but is not shown.
I restarted sChecklist again, and now the duplicated template which I could not rename - that doesnt show either - i.e. new lists are being created and saved, but they are not being remembered by the app.
I think I fixed it again
I edited the dat file to include the list I wanted (tiffs in screenshot above) and deleted the other unwanted duplicate.
Now when I add a new list it is saved on close