You can use this field to add specific messages to issue screens like create, edit, view or work flow screens. The panel contains, icon, title and the message itself. Since the message itself can be HTML you can put anything inside it with any formatting. Atlassian itself is using this technique to deliver some important messages to its users as shown in the following examples.

Feedback Policy

Provide Feedback on Issue Create Screen

There are 5 different message types you can choose from as shown in the following screenshot. Every type has a different color and icon to deliver a specific type of message. You should choose a message type suitable with the message content. For example suppose that you have a specific issue type of 'Backup Request'. You may use a warning message on the issue create screen to warn users about only the paths indicated in the request will be backed up on user's personal computer.

Configuration

Adding the 'Message Panel' custom field is similar to any other custom field. After adding it you need to configure it's type, title and message of course. This is done by clicking on 'Configure' link of the custom field.

On the newly opened 'Configuration Page' click on 'Edit Message' link as shown in the below screenshot.

This will open Message Panel specific configuration screen. Every field is optional, so you can only use title or only use message part if you want.

Type: Type of the message.
Title: Title of the message. It is optional but if you enter a title it will be displayed as bold line above the message.
Message: You can either enter pure text or HTML. There is no limit on the length of the message.
Label: On the issue dialog you may opt to not display label of the field. This will cause Message Panel to complete width of the issue dialog. The result will be similar to the screenshot provided for "Provide Feedback on Issue Create Screen" on the beginning of the page.

Every time you save, preview will be updated accordingly.

You can also use HTML tags inside message area for creating more rich messages as shown in the following screenshot.

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