The existing catalog of smart use case stereotypes is quite complete and is valid in a wide variety of (types of) projects. Although it is only rare to find new stereotypes, please feel free to add your own stereotypes.
In case you do encounter new types, our suggestion is to proceed with the following steps:
- Name stereotype. Name the stereotype according to its behaviour.
- Describe stereotype. Describe this new types behaviour briefly in the use case description. Don't forget about other elements this particular type works with, such as domain objects or forms.
- Estimate work. Take one or two example smart use cases that have this stereotype, and estimate (in hours) the amount of work required to implement it. This of course is a team effort. Sum up all the works for all the roles in the team. Don't forget testing!
- Relate to other stereotypes. Relate this amount of work (in number of hours) to the work you would do to realize smart use cases of already existing stereotypes. For example, if it takes you 8-10 hours to realize a Manage smart use case (which is a 3 on the scale) and the example smart use cases of the new stereotype typically take you in the same range, estimate the new stereotype (by default) also at 3.