I use the highlight colours consistently across my references, e.g. yellow=objectives, purple=results,... It would be great to be able to search or export the hightlights by a specific colour. Or have the type of highlight (highlight colour, underline colour) appear in the csv export file.
The ability to organise annotations by 'category' (and the ability to label those categories/colours) would be very useful.
Also the ability to show only certain types of annotations - e.g. notes only or highlights only (or even only blue highlights!)