The database files used for aliases always store keys with a null byte appended to each. When you use editmap on such a file, your key will not be found:

% editmap -q hash list-aliases user
editmap: couldn't find key user in map list-aliases

This lookup failed because editmap normally omits a trailing null from a key before looking up its value. When looking up keys in aliases-style databases, you need to use the -N command-line switch to append a null to a key before a lookup:

% editmap -q -N hash list-aliases user

Some database files (other than aliases) also append a null byte to keys. These databases will appear with a corresponding -N in a K configuration file line. In such instances, you must use -N with editmap to match the K line's -N.