I often do that in my own songbook while learning a song. Even if I'm familiar with the tune, I may have difficulty reproducing it accurately, or I may want to try different variations, so I pencil in a line of melody notes below the words while studying it.

And I usually end up with a slightly different melody than what everyone else sings, so sometimes I leave the melody notes in place permanently. And of course rhythm affects how the melody works, so I usually underline stressed syllables in the text.

I once posted a song here in that format, with underlined syllables, chords above and melody below, using Courier font, but it was a lot of work.