Append Field Mapping - Can you enter values to populate field?

[KellyArmstrong]

I have a feature class that I am appending features to, from another feature class.

When field mapping, is it possible assign a value to an output field by somehow entering text/string that will populate it with?

[DanPatterson]

there is nothing available in the tool's parameters to do that

Append (Data Management)—ArcGIS Pro | Documentation