Grooming has been renamed to refinement for better fitting into the corporate vocabulary.

According to the Scrum guide, it is not an event thus we cannot attend it. Rather, refinement is an ongoing process (though likely will embody in the form of events, too). The Scrum Master is responsible for ensuring that refinement takes place, has the desired outcome and it does not cost an excessive amount of effort for the team.

When a meeting is organized with the goal of refining backlog items, the Scrum Master can benefit from attending it, e.g.:

• the best way to prepare for the next planning;
• good for understanding backlog items;
• good for learning about foreseen challenges.

Thus, unless the Scrum Master has multiple teams and/or an additional role to struggle with conflicting events, it is advisable to attend all Scrum meetings.