Design of cantilever slab in RCDC should be added and also slab supported by beams on its two sides and its other two sides free or only three sides are supported by beams and the other side free.
Hifor Slab design, RCDC identifies the slab as per the area bounded by beams on all sides. It should form a closed polygon to identify as a slab. the loadings on the slab can be assigned by user. Thus, if the cantilever slab is modelled in analysis file, RCDC doesn't identify as a cantilever slab as it doesn't qualify as closed polygon.there is an option to design cantilever slab ( one way cantilever) in RCDC. Even it is not identified by RCDC, user can add new cantilever slab on input form and design the same. if you want to design slab cantilever on one side is possible. as it is new added slab and not present in geometry, only details of the same slab is available in text schedule. In-plan reinforcement details and section details are not available. refer below snap,The case which you have mentioned, i.e. slab supported by beams on its two sides and free on one side, doesn't become one way cantilever. it would be combination of one-way and cantilever slab which is not available in RCDC.