There isn’t a direct counterpart. Instead of user-created tag collections, EagleFiler automatically creates a “collection” in the source list for each tag. Clicking on a tag source shows the records with that tag, and you can drag into the tag source to assign that tag to the dragged records. You can select more than one tag in order to see all the records that have one or more of those tags. For more sophisticated queries, you would need to use the search box. Going forward, I plan to add more general smart folders, like in the Finder.
To import pre-existing files or URLs, EagleFiler has the capture and capture with options keys. Also, if the text of your note already exists somewhere, you can select it and use the Import service (Command-%) or drag it onto the Dock icon. EagleFiler doesn’t currently have a hot key for typing in brand-new text, although this is possible via AppleScript (and you can assign hotkeys to AppleScripts, e.g. using FastScripts). A popular way to create new notes in EagleFiler from within LaunchBar or Quicksilver.