I don't know if this is a bug or if it is intentional or whether I'm just being dumb and not seeing it, but in the latest beta version it does not seem possible to deselect the "Restore previously opened files at start-up" feature.
In previous releases, it was the second tick box under Options -> General. Now, there does not seem to be any way of disabling this feature.
In my way of working, I often end up with half a dozen or so files open in the editor and just close TopStyle down when I have finished. Next time I come to use it I double click a particular file I want to edit and do not want all these other files opening as well. In previous releases I have always disabled this option, but this does not seem to be possible in the latest release.