David Eldersveld shows how we can reduce the point size of dots in POwer BI as of March 2019:
One of the Power BI improvements in the March 2019 Desktop release was reduced bubble size for the Map visual. I previously wrote about the benefit of the reduction in point/bubble size. I was unaware until recently that this change made it into more than the Map visual.
The ability to reduce the point size also appears in the Format options for the Power BI Scatter chart. Previously, you could change the size option from 0 to 100 under the Shapes area. As with the Map, the Scatter now allows you to reduce the size as low as -30. I did not see this mentioned in the March Desktop blog post. I must have missed it if it was part of a previous month’s release. In any case, if you were not aware that you could set the point size from -30 to 100with the Scatter chart, now you do.
For most scenarios, I think the dot size is probably a little too big. -30 is generally too small, but I’m happy that they offer us options to get it right.