I would just like to identify for reference purposes. Some lenses don't have a complete description (the brand is lost) and e.g. if you connect a Samyang fisheye to a Canon, it's doesn't have any indication of the lens used (the Samyang is 100% manual and has no connectors).
I understand i need Lenstagger for this?
If you only need it for reference purposes simply add the lens information inside LR as Keywords. You can then locate images shot with this lens using the Filter Bar's 'Text Search' using the lens keyword(s) you assigned.
You only need an EXIF editor like LensTagger if you want the lens information to appear in LR's various displays (Histogram, Filter Bar, Metadata panel, etc.).