There is no simple solution to add multiple databases with one application.
You can have a look into this Mendix module: https://marketplace.mendix.com/link/component/80498
The easiest custom implementation of multi-tenancy is to distinguish data objects by a certain attribute.
For example, add a long/integer attribute TenantId.
It is however tedious to implement this at every entity itself.
What we have done to fix this is creating one master entity with the TenantId and the access rules for that and inherited this master entity in every other
Thus, you have 2 or more objects as follows
– TenantId (long/integer)
Customer (generalization of MultiTenantObject)