• https://github.com/i-rinat/fragview
• http://davtools.sourceforge.net/#screenshot

Not supported. Duplicated files can be removed and hardlinkied using 3rd party software:

• rdfind is a program to find duplicate files and optionally list, delete them or replace them with symlinks or hard links;
• jdupes - can convert duplicate files in hardlinks or relative softlinks
• fslint - GUI tool (deprecated)
• fslint-unofficial - snap provided but doesn't work!
• rmlint
  • Nice feature to save state: replaying
  • Can save checksums to xattr for faster consecutive runs miscellaneous-options

Not for ext4:

• duperemove

rmlint /BIG/POOL --progress --xattr -c sh:hardlink --size 1M
 
cp rmlint.json POOL.json
rmlint /BIG/POOL --progress --xattr --size 20M --replay POOL.json

rdfind . -dryrun