If you have WKO4, just look at the Extensice FTP recommendation in Optimized Intervals.
If you don’t, the usual recommendation it gives me is around 94% of mFTP @ TTE length. If you can’t do it all in one go, just break it up into a long and a short or short and long.
What I’ll usually do is to take the TR workouts and modify them, especially if they are longer. If it has 60 minutes of SS TiZ, I might break it up into 2 intervals of 35 and 25 minutes, or 40 and 20. This is especially helpful if your TTE is on the lower side (35-45 mins).