You can add a table for dynamic checklists.
create table work_action_dynamic_checklists (
work_action_class_id varchar2(24) primary key,
work_action_type_id varchar2(3) not null
default '2' -- ???
check(work_action_type_id = '2'),
checklist_class_id varchar2(24) not null,
foreign key (work_action_class_id, work_action_type_id)
references work_action_class (work_action_class_id, work_action_type_id)
);
For that to work, you need to add a unique constraint on {work_action_class_id, work_action_type_id} in work_action_class. This guarantees that rows in this table always reference a row in work_action_class that has work_action_type_id = '2'.
But unless you implement other changes, too, you lose the ability to require a checklist_class_id for every row that has a work_action_type_id of '2'. (A CHECK() constraint can fix that in the original table.) You could attack that problem with triggers or updatable views.