Perhaps I haven't fully understood the problem, but  Recorder will accept the standard tetrad grid reference eg SY67A etc. Recorder doesn't have to have locations (either ones in the hierrarchy or the location name field)  associated with records.

Do you think these are perhaps 200m references ( ie 25 parts of a 1km square), rather than the more normal 2km square ( 25 part of a 10km square ?),  If they are then Recorder can't hold them as such. You could either convert them to 1km squares just by dropiing the letters or  spurious 100m refrences by dropping the letter  and  adding in zeros   to make the refrencea 100m references. Either way you could add a note (say in sample reference) giving the true reference. 

If the above is true or if they are genuine 2km tetrads in a unusual format then youi can convert them before they go in in say Excel. If you are on R6 version 6.17 or above then a batch update after import is another option (I wrongly assumed you were on 6.12, from the other post -  but see now that this is the name of the report not your R6 version).