There was a similar question asked here:

https://community.servicenow.com/community?id=community_question&sys_id=fa5607e1db1cdbc01dcaf3231f9619ca

The key is that there is a field type called UI List Action that is not visible by default.  And, as an admin, I was unable to make it visible. That required the maint role.  I tried adding the maint role to the admin role in our instance, and was unable to do so... It seems like the maint role highly locked down and not something that should be given to individual users. As a result, I'm not sure what you are trying to do would be supported --or at least is not a recommended practice -- based on the security set around locking down this functionality that clearly exists in some form.