Under the song title I type the key (related to the chord shape) followed by the fret location of the capo.

i.e.
If I am playing a song in Eb (true key) but using the D chord shape, the notation would be D1.
The chord changes over the lyrics would be D, etc.

For a tune in true key of Bb and using a G chord formation, the notation would be G3.
The chord changes over the lyrics would be G, etc.

However, it's really whatever works for you.