Yes you can ignore a component when doing design sync. Here's how to do it:
Open the design where you have placed the subcircuit/component that you wish to ignore
Select the component
Right-click and choose the menu: Component > Edit Component Artwork...
Set the Artwork Type to Null.
The component will have a "NULL" artwork and basically be ignored in the layout. You will however see the instance name for the component in the layout since it's there in the database, but no layout is drawn for it.
The component will have a "NULL" artwork and basically be ignored in the layout. You will however see the instance name for the component in the layout since it's there in the database, but no layout is drawn for it.