Not sure if you are asking about analysis or design.
By analysis, I mean the process which yields joint displacements, support reactions, plate element stresses, etc. Any FEA program like STAAD or RAM Elements will do that. Cantilever slabs should pose no problem since it is just a matter of meshing the slab properly and placing the supports or beams at the right places.
By design, I am referring to what RAM Concept does, which is, find the reinforcement arrangement required to support the loads from the analysis. If you are referring to this, you have to ask the RAM Concept support group. I know it designs elevated floor slabs, but whether there is anything specific about cantilever slabs which makes it difficult to design, I am not sure.