Sort custom Multi-Select Picklists within List Views

Workaround:

In either Salesforce Classic or Salesforce Lightning, create a Custom Formula Field with return type as "Text" (with the formula below) and use the field to sort the list view:

1.Create a Custom Formula Field with Return Type "Text" using the INCLUDES() function for each picklist value.

For example, a formula that checks for values "A", "B", and "C" would evaluate each value with INCLUDES(), concatenate the results with a semicolon separator, and return NULL for missing values. 

2.Replace Multi_Picklist_1__c with your actual field API name and "A", "B", "C" with your actual picklist values.

 Note: If there are several picklists, the formula can exceed the compilation and result in an error.