If I understood it properly, zbik suggests to run mrp scheduler planned action.

So instead of an automated action, use the scheduler as planned action.

If that is what zbik means, it is the workaround I am currently using, however I wonder how it should be done to create an automated action, which is relevant for my specific Odoo deployment

Additionally, there could be more requirements like sending a SMS to procurement to put them aware that POs might need to be raised, so learning how to implement automated actions is definitively worth.

I think it must be something simple once you know it, but unfortunatelly t is hard to find documentation related to automated actions.