Actually, when pushing workouts as outdoor versions to my wahoo i can customize the data fields and add %FTP.
The app does not yet offer customization unfortunately
Until this feature has been added:
As all of us are looking out for new challenging while working out: maybe just use some math on the go…
87% of 311 FTP at 187bpm cant be too difficult… 
Might be even motivating: 100% of 311FTP at 199bpm is definitely easier to calculate … so keep pushing!