Level mode should be used when you’re trying to determine what you’re really capable of. You are the one in control of putting out the power! This is why Full Frontal should be done in Level Mode. The constrained effort in Half Monty needs to be done in Level mode also, as you adjust your power output based on your pre-determined heart rate constraints.
Workouts that have quick interval changes (think Violator, the Shovel) are best done in Level mode. Any workout where your trainer is struggling to keep up with the power changes should be done in Level Mode. This will vary depending on your trainer model.
Every workout can be done in Level Mode if you choose! There are benefits to training in Level mode, just as there are benefits to using ERG mode. We recommend doing a few workouts in Level mode before attempting a fitness test so that you are familiar with how your trainer responds using this mode.
For more details about Level mode, please be sure to check out A Guide to using Level Mode.