Two ways ...
1. There are many Sigil plugins to speed importing and cleaning of Word Docs.
See the Sigil plugin index on this site.
See this plugin for one:
https://www.mobileread.com/forums/sh...d.php?t=274536
And here is another one:
https://www.mobileread.com/forums/sh...d.php?t=273966
Plus there is an ODT html import plugin, and a CustomCleaner plugin.
The plugin index is here:
https://www.mobileread.com/forums/sh...d.php?t=247431
2. Do what you used to do in BookView but do it with PageEdit. You can fire up Sigil and get an empty epub. Double click to get Section0001.xhtml in the Code View window and hit the button to launch it in PageEdit and paste into PageEdit just as you did in BookView. Make any simple editing changes there and save the file and it will appear in the CodeView Window which you can use to edit the xhtml or proof in it Preview.
This is why we created PageEdit and created a one push icon to launch it from within Sigil.