Yes, but I would like it to show in the actual signature:

Please be aware that the position @Amal. pointed out is more the actual signature than the position where you want the reason to appear: The signature panel displays information digitally stored in the signature field for machine reading while the in-document visualization can contain arbitrary nonsense unrelated to the digital signature.
Nonetheless, if you want the in-document visualization of the signature to contain a Reason line, you have to start by defining a custom appearance at the bottom of the signature creation and appearance dialog you show. In the dialog that opens when you click on New you see

Please select Reason in the configure text frame:

As you see in the preview, there now is a reason line.
Now save this appearance and use it when creating new signatures.