What is the best practice to maintain attribute domains when using Split in ArcGIS Pro?

Answer

A feature is split into two or more features when it is clicked using the Split tool or when a sketched line or the boundary of another feature crosses it. When the tool is used on an attribute feature, the values of the original feature are copied to the new feature.

The best practice to maintain attribute domain data when using the Split tool is to configure the correct split policy for the domains in the selected data. Setting the split policy for the domain properties allows control of the attribute value in the output. To add a split policy to an existing attribute domain, use the Alter Domain tool. Refer to ArcGIS Pro: Alter Domain (Data Management) for instructions and more information.

Note: 
Applying the Split tool to domain-constrained attributes without first selecting a split policy causes the attribute information of the original and the new features to be erased as the values of the output are not recalculated.