Feature summary (what you would like to be able to do and where):
When using Multi-Content-Revisions content models, the page will be edited in single-slot mode and the content from the edit form will be saved into the assigned slot rather than the default slot . Of course, this only works, when the page's content model supports multiple slots

If this was to support multiple slots for multi-slot mode, the syntax would then be slot[]=

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):

Benefits (why should this be implemented?):
Afaik, currently, only the default slot can be preloaded into or would the edit form be opened in multi-slot mode otherwise?