In Odoo 10, I can create Quotation when viewing an Opportunity. Also, when creating a Quotation, we can link it to an Opportunity.
Just try Odoo 11 and the button to create Quotation in Opportunity view is gone. The Quotation can not link to an Oppotunity neither.
Can I enable something to make the CRM flow work like on Odoo 10.
Odoo 11 still hold this functionality. There is a "New Quotation" button in the Opportunity and the quotation created from it has a link to the parent opportunity. The Opportunity field in the quotation is visible in the "debug" mode. Please check it.