Publication rights are associated with the account status at the time of export. So, if you exported a figure while on a paid license (not during the free trial period), you can continue to use it in publications once you downgrade.

Ensure you download a publication license before downgrading or canceling your subscription! Please refer to this article: How do I download my publication license?

A heads up: if you need to make changes to the original figure after you downgrade, export features and publication rights will be limited again.