There is presently no specific way to trigger a revision of an entity, this just happens automatically as a part of the entity's lifecycle.

Presently, the suggested solution would be to use conditional auditing for this; however in designing a better conditional auditing approach for Hibernate Envers 6 using annotations rather than custom listener implementations like the documentation suggests today, I uncovered that conditional auditing can be problematic for ValidityAuditStrategy users when you elect to not audit the initial INSERT operation for an entity and later allow an audit for an UPDATE operation.  So long as the initial INSERT is allowed, there is no issue, so beware if you wanted to use this route and you use the ValidityAuditStrategy.  If you're using the DefaultAuditStrategy, there is no problem with conditional auditing.

Another option you didn't mention could involve the use of two entity types.  Imagine for the moment you have two entities which derive from the same mapped superclass like as follows:

@MappedSuperclass
public abstract class AbstractEntity {  
  @Id
  private Integer id;
  private String data;
}

@Entity
public class DraftEntity extends AbstractEntity {

}

@Entity
@Audited
@AuditOverride(forClass=AbstractEntity.class,isAudited=true)
public class SavedEntity extends AbstractEntity {

}

The idea is that SavedEntity acts as a shadow-copy of your drafts.  That way users can make any number of repeatable, non-audited changes to the draft entity and when your business process dictates a snapshot is to be taken, you merely copy the attributes from DraftEntity into the respective SavedEntity.  From there, Envers keeps a running audit history of all changes made to a given SavedEntity.

Yes you can do that with the @AssociationOverride annotation.  From the java documentation:

May to be applied to an entity that extends a mapped superclass to override a relationship mapping defined by the mapped superclass.  If not specified, the association is mapped the same as in the original mapping.  When used to override a mapping defined by a mapped superclass, AssociationOverride is applied to the entity class.

Furthermore the documentation points out if the original mapping uses a @JoinTable, the override must also explicitly include the joinTable element of the @AssociationOverride too.

See AssociationOverride (Java(TM) EE 7 Specification APIs)