I've tried to populate a text automatically to the "Description" field which is a tinymce on Jira by the field configuration function of Jira, and once the user clicks "Create" button to open a dialog to create the issue, the text should be populated in the "Description" field.

I executed the following code on the console of browser and it returned null:

document.getElementById("tinymce");

But once I use the inspect function of Google Chrome and Microsoft Edge to focus on the tinymce first and then execute the same code on the console, it returns the tinymce element.

How to be able to access the tinymce once the user clicks the "Create" butotn on Jira?