If you have created an Insights report that you would like to export, you can select the download CSV button in the upper right-hand corner of the report. At this time, there is a 1000 segment limit on Insights exports, so for extremely high cardinality properties the export may not return all segments, but it will return the top 1000.
The ability to download a CSV of your Insights report data is only available to members on an Enterprise plan. To see which plan you are on, please check your Billing Plan under Account in your Mixpanel project. For more information on the different Engagement plans, please see our pricing page.