I don't know of a way to customize all the quantiles that are shown in a Distribution report. However, there is a platform preference (File > Preferences > Platforms > Distribution) called "Set Quantile Increment". If you only want the 95th percentile, you can check the box for this preference and enter a value of 0.95. This will give you a Quantiles report in Distribution that has only two rows (0% and 95%). If you specify a smaller value (such as .1), then you can get the quantiles at each 10% increment.
Michael Crotty
Principal Statistical Writer
Manager, Statistical Documentation
JMP Development