Cost Explorer dashboard has following 3 tabs:
On giving normal access to Cost explorer dashboard, BOM tab access is automatically granted to the user.
Other 2 tabs are accessible via validation app. Hence you can give access as App Validator = Cost Explorer under Custom properties in user profile and inform the user to check the application\dashboard in Validation stream via below link,
https://qliksense.solvay.com/solvay/hub/stream/f40ce7ec-0a28-442b-9084-e7977e36ec1d
Reference ticket: https://sbs-support.solvay.com/a/tickets/5304132