I need more details.
Which visualization are you using? I think that you are saying that you have added multiple dimensions to this.
I just tested with a bar chart and I was able to set a Top limitation on each dimension separately. So on Dimension1 I set it to Top 5. I only see five sections now.
Under that I set Dimension2 to Top 3. So now I only see 3 bars in each section of 5.
What are you trying to do?