Modifying the BOM does not change the MO, neither does an engineering change in PLM. Someone on github said something about removing create="0" from the view but that is only part of the change, all sorts of errors occur.
https://github.com/odoo/odoo/issues/14689
The official answer from the webinar below seems be to modify consumed quantities in existing MO, but create new lines in a new BOM in a new MO. But that new MO must also consume the final product produced by the previous MO.
https://www.youtube.com/watch?v=beBakBlHcLY
Still, this is cumbersome and unintuitive. We are producing buildings which takes weeks and plans change during production.
The 'Consumed' column in your screenshot should be editable - at this stage I believe you can only adjust quantity, not add/remove products.