Removing duplicate files in organizer

Are you meaning exact duplicates such as you get when you go file > duplicate and Elements creates a copy ?

The only way I know to remove them is to individually select them and go edit > remove from organizer, and check or uncheck the box that says "also remove from hard-drive"

flyboy, you are most welcome! Post back if you need any further help.

There are many duplicate files deleter softwares, but none do work with the Organizer. In other words, you may be able to find and delete duplicates, but that will not update your catalog. All deleted files will be shown as 'disconnected' in your catalog and you'll have to delete them from the catalog.
Deleting a big number of files in the catalog may abort in older Elements versions or will be very slow. If you delete outside of the organizer, try to delete small batches to avoid the trap.

I have tested various duplicate manager softwares. They are generally smart enough to let you choose and combine different criteria like filename, date_taken, size, sometimes visual similarity like the organizer,  and more. They also let you define criteria to select which criteria to use to delete such duplicates. They would recognize the suffix if set with correct parameters.

You should keep in mind that there is nothing automatic and perfect. Some free softwares may introduce malware in your computer. Almost always you have to search more to decide which is the wrong item...

Remember that the downloader should not import duplicates in the definition of the organizer, mainly files with the same size in kilobytes and date_taken. Files with different file names can be recognized as duplicates.

With scans, the only useful criteria is visual similarity. I have many duplicates of old family photos coming from various sources or scan sessions. Choosing between 6 'versions' of the same shot is a tricky job. I most often decide to 'stack' the different versions instead of wasting time in searching which one to delete.

When you get duplicates with a suffix, you should search immediately the source of the problem. Let's say you have two catalogs. The downloader will see no objection to download from your card in a catalog, even if you have already imported in another one. To avoid copying with the same name in the same subfolder, the downloader adds a suffix. If you switch to the previous catalog and try to import from the folder, the 'Import' feature will recognize the duplicates and won't catalog them. Just an example...

Yes, the 'search for duplicates' in Elements Organizer is ONLY by visual similarity. The resulting display lets you see the suggested similar files and you can review the suggested stacks, highlight the ones you want to stack (ignore the non duplicate ones) and stack them.
Once you have stacked your duplicates, you have a clearer browsing space for further visual searches.
To get rid of the bad duplicates, you have to select the best version and set it as 'top of stack', then you 'flatten' the stack.  Very often, you don't want to delete 'similarity' duplicates, you only want to 'stack' them.
Frequent situation: you are working in your laptop with raw pictures. You edit them on the laptop and create jpeg version sets. You import both raws and jpegs to your destop. The 'version sets' are not recovered by the import, since they are only recorded in the catalog. So, you select your folder, run the visual search and instead of version sets, you recover stacks. That's enough to only show you one version (raw or jpeg) to browse more comfortably while keeping a link between raw and jpeg.