One thing that I have seen others do is to create a kind of footnote system in their laptop document so that any formula or diagram gets a reference number then

One thing that I have seen others do is to create a kind of footnote system in their laptop document so that any formula or diagram gets a reference number then they quickly grab the pen and paper and jot the formula/diagram down then straight back to the computer. Then after the lecture just digitalise the footnotes. Really depends on how much of the lecture is formulas/diagrams to text I suppose.