Tool for detecting and removing duplicates? [Available in 8.10.18]

My Duplicates occurred when I upgraded from V7 standalone on my least used machine to V8. I was already using V8 on two other Macs an iPhone and two iPads. That upgrade process was terrible. It wanted me to create a new 1Password membership (I already have a membership which there was no obvious way to connect to.). I ended up downloading V8 and installing it. It said I had to convert my V7 data to V8. It was not at all clear that I could have just skipped that step. Now I've got about 800 duplicates. The upgrade process needs to be more clear so duplicates are not created in the first place. We also need a duplicate finder/remover tool.