I pulled up a new song on piano and started looking over the sheet music when I saw Quarter Note = invisible. Does anyone know what this means? And what it changes to the sheet music?
I think we can only guess, because it is not a normal marking.
Looking at other transcriptions, it appears that there is no fixed tempo for the piece, and that it is played with rubato, a specific way of speeding up and slowing down. This makes me think that the marking in question is meant to indicate that the tempo for the piece is not clear, and "invisible" might be a mistranslation.
I suggest looking for a different transcription.