This snippet to rollback multiple payroll actions. Handy in a test environment.

for r in (
Select payroll_action_id from pay_payroll_actions
where
order by 1 desc
)
loop
py_rollback_pkg.rollback_payroll_action
(
p_payroll_action_id => r.payroll_action_id,
p_all_or_nothing => FALSE,
p_dml_mode => 'FULL'
);
end loop;

The API pay_balance_adjustment_api.create_adjustment is functionally the same as the Adjust Balance form. An element entry is created (creator type and entry type = B), non visible in the element entry screen. The creator id points to an assignment action. A payroll action (B) is created, with one assignment action, and one single run result.