What do you exactly mean?
It's default feature: each separate session defined in KiTTY (and also PuTTY) has own setting in Session -> Connection -> Data -> Login details: Auto-login username, you can store in this field everything you need.
Another one feature is in basic Session -> Host Name (or IP address) field: you can enter value in pure SSH form - username@server.com, and save session with name of your choice. Later it will use stored username in the same way as described above.
What do you exactly mean? It's default feature: each separate session defined in KiTTY (and also PuTTY) has own setting in Session -> Connection -> Data -> Login details: Auto-login username, you can store in this field everything you need.
Another one feature is in basic Session -> Host Name (or IP address) field: you can enter value in pure SSH form - username@server.com, and save session with name of your choice. Later it will use stored username in the same way as described above.