Inside CRM I can perform a 'Mass Update' to a Multi Pick List which gives me two options: 1) Overwrite and 2) Append. Append allows me to 'add' an additional value to whatever might currently exist in the field.

However, if I now want to import data from a CSV file, when I map data to a Multi Pick List, I do not see any option to "Append" which leads me to believe existing values will be overwritten. Am I missing something here? I have to believe that I can simply Append when performing an import?