Great to see there is some interest in having Significant Wave Period and Peak Period displayed on Windy!
These are the most useful for surfers and better than mean period fields.
They allow the user to much more clearly distinguish between swells and track them over distances.
In the ECMWF paramater list I can see ( https://codes.ecmwf.int/grib/param-db/ ) "Swell Peak Period" and "Wave Peak Period", the former being more useful