if you want to to set default value for new records:
A handy way to do this on models where you're creating new records is to just create conditions on the model for your default values, e.g. on an account page where you have a new contact model have a condition on this model where AccountId = the Id from Account Model, one where Mailing Street = BillingStreet from Account Model, one where Title = Business User etc.
Another way is to use the action framework when you're creating new records (like when a user clicks on a button, opens a drawer or a popup) to activate a set of conditions and query a model and/or create a new row on a model with default values x,y, and z (you add the default values right in the action framework and can use merge syntax to bring in values from other models.)
Another way to do this with the action framework is to use the update field on row(s)action type.
Does it sound like any of these options will work for you? What exactly do you want to do?