Migrating Lat/Lng to Blogger Geotags
Blogger-in-Draft Location Editor
Enter a space separated Lat Lng pair into the search box of the Blogger-in-Draft location editor and click Search. This will zoom the map to the correct location but leave the Location link name blank. Zoom out (using the - button), the Location link name should now appear.
Adjusting the Location String
The Location string is determined via the reverse geocoder which will sometimes result in Unknown Location. You can adjust the Location name by clicking on the Location Link under the search box (next to Location:) and entering the desired Location text.
When I first tested direct lat/lng entry it didn't appear to work correctly (user error? Bug Fix?). Sometimes the result would shift back to the reverse geocoded result instead of the Lat/Lng in the search string.
Finding a Lat/Lng
There are lots of ways to get the Lat/Lng of a location/address including Wikipedia (good for tourist locations) or by extracting the data from geotagged photos (from a mobile device or automatic geotagging software).