[KevinH]

Huh? You should really read the Sigil User Guide chapter on Spellcheck. You will see there are two different modes of spellchecking. The first is real-time as you type red squiggle underline marking of unknown words. You can right click on any underlined words and if there are suggested replacements you can select them.

The second mode to use the Spellcheck Dialog Tool. You can launch it via the menus or hit the icon with checkmark and ABC on it).

It will generate a sortable list of unknown words. You can select any word, get suggestions, choose to ignore it, etc. It can nicely navigate you to where the potential incorrect word is found so you can see it in context.