I've asked for this before I believe and am asking again. It would be very helpful to be able to add tags directly from the context menu. There should be an "Add Tag" function which opens up a field in which one can enter tag(s). I know it can be done via notes and that labels can be used somewhat that way too. But these lack the immediacy of just being able to tag sentences, paragraphs or sections while reading.
With tags so immediately applicable, it would be easy for users to tag material throughout their libraries and then search and retrieve those when needed.
