Mid-size notebooks lag in browser rendering / responding to simple navigation requests. I've seen many times that once notebooks grow up above a "small" size, rendering lags can happen. Running latest Chrome with a decent Intel i7 processor. For example, a notebook I am working on has around 35 paragraphs and is just 145k note.json (there are no big data tables - nothhing crazy), starts lagging quite a bit which doesn't help with UX.
I've noticed paragraphs in HTML code can be burried 10 levels deep in DIV-DIV-... nesting. This could be the root cause? Browser might have hard time calculating all those nested CSS styles etc? I know some colleagues of mine start splitting notebooks into separate notebooks when they see this issue. Not sure if this is a known issue and if everybody else experience the same?