I'm familiar with nvim-lightbulb and use it myself. Can't remember what was the reason I thought having the same/similar functionality in lsp_lines.nvim would be superior over that particular plugin though. Probably that having the information displayed as part of the same virtual line stack as the diagnostics so it would be more obvious than having the info in a separate place.

I don't know if it goes out of scope of the plugin, but it would be nice to get info on having some code actions available at the bottom of the list of virtual diagnostic line. It usually indicates that some of the errors might be automatically fixable. Mapping the actions to specific diagnostics would definitely go out of scope of this plugin but a generic "Hey, this line right here? It has some issues, but there's also some code actions available that might help" would be nice.

I would be interested in this as well. Virtual lines tend to mess up the cursor placement if there are plenty of adjacent lines with diagnostics on them. It doesn't really matter that a floating diagnostic window would hide lines under the current line since they usually aren't relevant when you're looking at diagnostics.