In order to customize the properties that are imported from your Salesforce dataset, you can click the Custom Configuration option when importing your data. In the resulting modal, you will have the ability to select the specific properties to be included.
Properties that are to be included need to be checked and properties that should not be included should be left unchecked. Once the desired properties are selected and the Update and Check button is clicked, Mixpanel will validate all objects to be imported and ensure that none have more than 250 properties.
If any validation fails, you will receive an error message indicating the Salesforce objects that have more than 250 properties. You will need to ensure that each object has less than 250 properties selected and after doing so can attempt to re-import the dataset. After the configuration is complete, the dataset will be imported and refreshed every 12 hours.