The journal should have a section for finished quests. I'm really tired of trying to remember if I did a particular quest and then wasting my time starting out on it only to discover that yes, I already did it. The journal is a festering sore on SotA.
Yeah sadly our current Quest System Journal, (most) all the entries for quests you have previously have done (Knowledge Journal) have disappeared. There is no way to see what quest you have finished currently. Will probably have to wait for the new Quest System 2.0™ and hopefully there will be a way to see quests we have already completed.