I do have something of a feature request/bug report.
I've encountered a multi-chaptered story with html broken enough so that Sigil couldn't handle direct importing of the code. So I've used
dotEPUB to download individual pages, as it did help with formatting a bit. I used this plugin to combine them all into one story, and then wanted to use Sigil to edit it to make it look presentable/delete unnecessarily generated stuff/have actual chapter names instead of just the story title for every single one of them etc. The problem was that even though all the chapters originally appeared in order, Sigil can't recognize it and arranges them almost randomly. So even if I were to do nothing but save the file once it was opened, it would be messed up. Trying to reorder them just breaks it up even further.
Would it be possible to make these files editable, and perhaps have an option of arranging them like a true book instead of anthology? And, perhaps, if you have time, remove extra title/disclaimer pages generated by dotEPUB?