You can easily create your own easings and use it for deforming terrain.
Step 1:
Add a new value to the enum Easing inside CurveArchitect/Scripts/Objects/Easing.cs
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Step 2:
Add logic for your new easing inside the CurveArchitect/Scripts/Utilites/HelperEasing.cs.
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Now your new easing should appear in the drop down menu located in the same row as terrain blend width.