Is the ability to list the highlights/annotations in DT a feature of DT 3?
Yes, this is a feature of DEVONthink 3.
Can these be exported?
It’s unclear in what way but look at Tools > Summarize Highlights.
One of the big problems is that DTG has been relatively neglected and needs some love (one can’t highlight text, for example).
DEVONthink To Go has not been neglected. It is on a different development cycle as DEVONthink 3 and we have marshalled our resources toward getting 3 to a gold master public release.