C4C Sales Quote: Change Default E-Mail Subject

Hello experts,

we are currently struggling to change the default E-Mail subject which is generated for Sales Quotes:

We already changed the E-Mail Body and uploaded our html file under Administrator > Form Template Maintenance > Sales Quotes > Actions > Create E-Mail Template. That is working as expected but we didnt find a way to change the generated E-Mail Subject. Any ideas or is it not possible at all?

Best regards

Max