Just as it was with Smart Reporting, Helix Dashboards cross-launch settings to Smart IT parameters must be enabled as per the official docs stated below.
https://docs.bmc.com/docs/smartit2105/setting-configuration-parameters-for-smart-it-1002910325.html
 

Default Parameter value

helixdashboard.url

Description

By default, this configuration parameter is empty and you cannot see Helix Dashboards in Smart IT. You must put the url of BMC Helix Dashboards in this configuration parameter to get Helix Dashboards in Smart IT. To make this configuration work properly, you should use the same BMC Helix Single Sign-On for Helix Dashboard (Advance Digital Enterprise) and Helix ITSM. You can also set up BMC Helix Single Sign-On authentication delegation through Open ID Connect (OIDC) between ADE and ITSM BMC Helix Single Sign-On. Without this configuration, when you click Helix Dashboards in Smart IT, you get the login page of Helix ITSM instead of BMC Helix Dashboards.

Example:
 

Parameter	Value
helixdashboard.url	https://tenant-site1-dev.onbmc.com/dashboards/

This is how it looks from Smart IT 21.X



Note: if required, delete the "reportingServerURL" parameter on the configuration to delete the previous Report button to avoid confusion. Parameter must be deleted at all and not just clear the content.



See also: BEST FAQ on Remedy with Smart IT Configuration & Settings