In case you just need this 4.518 alpha (uploading now) adds a simple Finder Extension that can be configured in the "Automations, Named & Other Triggers" section in BTT.
Here is an example on how to use it:
FinderExtension2.bttpreset (11.7 KB)
When the context menu item is triggered, BTT will make these variables available that can be used e.g. in terminal commands or scripts:
BTTFinderContextMenuTargetPath (the path of the current folder)
BTTFinderContextMenuSelectedItemPaths (the paths of the selected items, separated by ;; )
BTTFinderContextMenuTriggeredUUID (the UUID of the context menu item in BTT)