Adjusting the intensity of a workout

Is there a way to adjust the intensity of a workout during a workout, or just before the workout is started?

I’m asking because my FTP is mostly based on outside rides on the road bike. When I do a workout indoors or on the TT bike (or both), I’d like to scale the intensity down without having to edit the workout itself.

Nice question, I’m interested to in this topic

What many do (one athlete described this on the FB user group) is to adjust their fitness signature in advance of the workout. In their particular case, they were using different power sources and needed to adjust the intensity down as a result. You can do the same thing on a temporary basis. Make an adjustment to your fitness signature and then load the workout. Adjust it back afterwards.

Note that during the workout using the Garmin Player app, you can adjust each interval interactively. Not exactly what you’re looking for but worth noting.