Currently, a relationship can be set up between a minimum of 2 services, up to 20 services for each relationship type.

It would be great to have the possibility to link more than 20 services per service.

However, you can add 20 Service Relationships with type Depends on and Used by. In total, you can create 40 such relationships for a single service. Unfortunately, you cannot go beyond this number and the change to this number has to come via this suggestion ticket.