Hi @Andrey,
Importing value change history for a custom field will give you information on when the values changed. Retrieving the user who made the changes is more challenging.
You can have a look at this eazyBI community post for importing issue activity - Count User interaction with Issue. That is a more generic approach to importing all activities. Still, you can try to alter the JavaScript code to only look at the changes made to the specific custom field.
The eazyBI documentation page has more information on JavaScript calculated custom fields - https://docs.eazybi.com/eazybijira/data-import/custom-fields/javascript-calculated-custom-fields.
Best,
Roberts // support@eazybi.com