I often use the "Browse" part of the site to find lessons to watch - and usually watch lessons in an ad-hoc fashion.
However some days I want to methodically work my way through any lessons I haven't yet watched, to continue my learning and fill gaps in my knowledge.
In the latter case, I would find it very useful if there was a filter to show lessons I haven't yet watched. I am sure others would also find this useful.
Hope this request reaches you well, and love the site,