Revlin - Assuming you have Order bars set, and the bars are ranked from left to right in descending order, use the Split-by drop down and choose 'Fit to screen' to the right of the measure you are splitting by. This will give you the option 'Exclude values by fixed limit' which allows you to use a slider to set the maximum number of bars to display, e.g. 10 for top 10.

If you do not want the other values to be grouped into an Other bar, use the small down triangle to the right of the unique values selction to drop-down more options and untick 'Include excluded values grouped as "Other"'.

Thank you tjbate. Much appreciated!