After burning almost straight up until all the fuel was spent, I coasted to the apoapsis without timewarp (max 3x time accelerate). After reaching apoapsis, I tried to create a manouver node on the decending part of the ‘orbit’ (the flightpath being suborbital). I couldn’t click on the orbit or hover over it(no faded sphere appeared).
Maybe relevant info:
1. No Stages with engines left
2. In normal time mode
3. Locked onto surface speed prograde
Edit by pedro16797: They can be added, but it is extremely hard to do in some regions of the trajectory.