Duplicate entries after imports

Until 1Password adds a function to merge Items, we have to do so manually.

Watchtower identifies reused passwords, so can help identify different Items for the same thing which are not duplicates, however that may not be particularly helpful compared to sorting and searching.

The desktop client and browser extension don't have the kind of sophisticated filtering which you mention. You could try building your own using the command line interface (CLI), but if you only have twelve (or fourteen if you're a baker) redundant Items, then it's probably not worth the effort.