Is there any limitation for field to put in a default value ?

[光野 かおる]

Hello, Jira community. 

I currently use explanation field for developers to put in the explanation for the issues. 
In this way we can easily remember what we did during this issue looking back.
And I set the category that person in charge should fill in and this category goes for all issues. But to save time I want it to be a default value in explanation field. 

So what I want to ask is ,

How can I set a default value in this explanation field.
I checked the "Add a context to a Custom Field" but I can not find explanation field from it.

The part I'm stopping at is down below.(yellow highlight)
I could find other fields but I can't find the "explanation field".

Do you know if there is a certain limitation for specific fields to add a default value?

[Trudy Claspill]

This question is already being addressed in this thread

https://community.atlassian.com/t5/Jira-questions/How-to-set-a-default-text-in-a-explanation-field/qaq-p/2898134