We have added an option to Crew Duties page to assign SIM duties which will automatically appear in a section SCHEDULE. Right below the list of your defined duties (in a section Duties Setup) you can find an option to assign Simulator duty to appear in a section SCHEDULE.

In the roster, SIM duty appear as a blue aircraft icon on white background

It is possible to add more than 1 of the bottom-list duties on the same day. If it's the same duty - click an icon when a pop-up window shows up, after selecting duty. If it's a different duty on the same day (i.e. Office and Simulator) simply click on the same day in the roster and select another duty - Leon will show both duty icons