Hi partner,
You only need to enable quick create forms in the entity settings of the default solution.
Go to Settings > Customizations > Customize the System, Data > Entities, select Default to All, open entity Quote line.
Click Settings > More Settings > Create and update settings, check 'enable quick create forms'. Save and publish.
The entity Quote Line has an OOB quick create form, and it is added to the Sales Hub app by default.
If you can't use the quick create form after you have enabled quick create forms, check if the Quote Line has a quick create form and if it is added to the Sales Hub app.
