Creating external follow-up sales orders will be disabled if alternative items exist in the sales quote.
The Alternative to Line needs to be reset and the item cancelled if it was not ordered by the account.
The action Create External Follow-up Document will be enabled once the alternative item reference was removed.
SAP Cloud for Customer
This is a system Limitation.
This is the current system behaviour.
Sales Order, Follow-up , KBA , LOD-LE-CQP-CO , Lean Sales Orders , Product Enhancement