macOS 10.9 and later have built-in support tags in the Finder and other applications. EagleFiler syncs its tags with the system automatically. Each file has the same tags in EagleFiler and the Finder, and the tags are searchable in Spotlight.
Tag Syncing
Differences Between Tags in EagleFiler and Finder
Disabling Tag Syncing
Some people prefer not to sync their EagleFiler tags to the Finder. Syncing takes time, which may not be worth it if you rarely use tags in other applications. Or, you may prefer not to see your EagleFiler tag names when adding tags in the Finder if you only use those tags in EagleFiler.
To disable tag syncing for all libraries, click here. To re-enable tag syncing, click here.
You can also disable tag syncing only for certain libraries by specifying their filenames (without the .eflibrary) using this Terminal command:
defaults write com.c-command.EagleFiler DisableTagSyncingForLibraryNames -array "MyLibrary" "SecretLibrary"