Workflow variables updating on Oracle Apex 24

I am learning Oracle Apex 24, and creating a workflow ( created a human task / task definition ). I am able to create parameters initialized once when the workflow started but they are read only for the rest of the flow.

I am unable to add variables along the workflow to update them from one task definition to another.

I have tried many methods but non of them worked. Any suggestions?

i am using the API but its giving an error:

DECLARE
    l_workflow_id  NUMBER;
 
BEGIN
    SELECT workflow_id
    INTO l_workflow_id
    FROM apex_tasks
    WHERE TASK_ID = :P5_TASK_ID;
 
    apex_workflow.update_variables(
           p_instance_id => l_workflow_id,
           p_changed_params => apex_workflow.t_workflow_parameters(
               1 => apex_workflow.t_workflow_parameter(static_id => 'V_START_DATE', string_value => sysdate+10)));
END;

error:

APEX - APEX.WORKFLOW.UPDATE.NOT_ALLOWED 

Any help please ?