This idea is related to "Ability to deactivate/hide project templates in TE", but has a different goals.
Sometimes there is a difference between the type of projects which would be created by internal teams (creating projects in TE), and external customer requesters (creating projects in the customer portal).
It would be great to have a setting/check box which allows us to not display a particular project template in the Customer Portal.
This would complement and extend the idea of deactivating project templates altogether.
(Note: this is in place in TMS + Mantra and is frequently used)