How to design learning tools for severe and profound and/or multiple disabilities children?

Good luck.

I appreciate your quick and helpful answer.

It's important to assess the individual to identify their most effective/preferred sensory modalities; then to design teaching tools around them. Many of these children need to 'learn how to learn' as the strategies that other children use may not be accessible to them. The Intensive Interaction approach is very helpful for your targeted children. Most of the research is qualitative, though a few quantitative studies have been undertaken. However, given the highly individual nature of such youngsters, qualitative studies seem very appropriate to you. A good resource on the approach is Hewett, D., Firth, G., Barber, M. & Harrison, T. (2012) The Intensive Interaction Handbook. London: Sage.