Yes, this is configured on the engine level. The UI apps do not have multi-tenancy enabled. You could tweak the engine configurations (the UI apps are Spring Boot apps, so configuration is possible), however the UI would also need small tweaks to allow for multi-tenant logins, etc.
Do we have any configuration for Flowable-UI or which class needs to be tweaked to implement MultiTenancy Approach for Multiple Schema Shared Engine Approach.