[DiapDealer]

There are no features missing from the Sigil version compared to the calibre version (of the Span/Div Editor portion of the toolbag), that I'm aware of. If you're talking from a strictly aesthetics standpoint, there is already an overhaul of the plugin's UI in the works.

Not only COULD a goodly portion of the code from the calibre version be used in the Sigil version, a goodly portion of the the code already IS (and always was) used in the Sigil version.

Can you explain what features of the Span/Div Editor portion of my calibre Toolbag plugin you feel are different (or missing) from Sigil's Tagmechanic?

Keep in mind that the visual diffing capabilities of the calibre plugin are only possible because calibre itself provides that functionality--lock, stock and barrel. My plugin just "flips a switch" to display it. In that regard, there is unlikely to ever be a similar feature in the Sigil plugin itself. Sorry. Use Sigil's checkpointing feature if you want to see visual diffs of the changes a plugin makes (and to revert them if necessary).