Filter service accounts / non-user accounts of search results in SharePoint ONLINE

I'm developing SharePoint ONLINE "Employee Directory" where I can get all the information of the users along with the service accounts. The requirement is not to display service accounts or non-user accounts (for example, accounting@domainname.com, marketing@domainname.com, etc.) in the web part of search results.

There is a new custom attribute in AZURE Active Directory with the name "Employee ID"that distinguish whether the user account is a service account or a normal user account." How to assign that Azure AD attribute to the property of the SharePoint ONLINE user?

I followed this link (https://thomasdaly.net/2016/01/16/hiding-people-from-people-search/) but the newly created managed property does not appear in the Property filter drop-down menu of the Change of result of search query.

Can someone please help me solve this problem?

Thank you very much in advance.