Have you got more than one version of Sigil installed?
When both those screenshots taken was the epub opened the same way?
You could have *.epub filetype to open with say Sigil v0.5.3, but have a shortcut on desktop for Sigil v0.5.9.2 (beta).
So depending on how you're opening, you could have different version opened, thus the difference in layout/features.
|