When rebuilding our Scoring Models in Real-Time Marketing we noticed that currently only 6 tables/table joins can be used in total. Since there is a number in the total number of Scoring Models, which can be created as well, we highly recommend to increase this number. For us internally, going through some relationships to "get to the data", 6 tables or joins is not enough. We think an appropriate limit would be 15 joins as we have it with advanced finds in Dynamics 365.