Originally Posted by theducks
I still think a save 'as is' is needed.
It would not hurt, as long as the consequences were well understood, in the case of saving a corrupt file. (How about giving the option to rename the saved file?)
Save often, under different filenames as necessary. Especially before you try something experimental.
Then, Sigil should provide the options to "recover the crashed file" or not. In the latter case, open the last-saved, known-valid file.