groundfloor,
As Old Smokey said:
It's all pretty straight-forward really. If an operator, due to their own particular set of circumstances, environment etc., wishes to change an operating procedure from that laid down by the manufacturer, they must approach the manufacturer with the proposal.
My bolding.
Which coincides with what I tried to tell you in my original post:
If the procedure in the AFM requires amendment, this must be carried out by the manufacturer or other organisation approved to make such amendments prior to changing the checklist.
Is really is pretty straight-forward groundfloor, particularly if you follow this STANDARD way of doing things.