You can create at least 20 groups within the schedule as I have personally tested this this afternoon. There is no documentation I can find which has a hard limit - but this will cover your requirements.
There is no real workaround for this currently. It is expected that functionality such as recurring shifts will be introduced over the course of the year and before StaffHub is retired in October 2019. You could copy and CTRL-V paste shifts which may speed it up but I don't think this will help a great deal if shifts are at different times.
Hope that clarifies
Best Response confirmed by
alanh1123 (Occasional Contributor)