How to add issue "Assign" pop up window and its button on issue screen?

[Nikhil Darji]

I want to have a "Assign" button as per the attached screenshot.
On click on that Assign button, pop should open as per the attached screenshot.

Please help me to achieve this functionality.

Thanks in Advance...!
Image 1

Image 2

[Utkarsh Agarwal]

Hi @Nikhil Darji ,

I do not see the attachment!

However, if you are talking about transition screen, refer: Map a screen to a workflow transition in Jira 

Kind Regards
Utkarsh

[Jack Brickey]

No screenshots.

[Nikhil Darji]

Hi @Jack Brickey 
Kindly check now.

[Jack Brickey]

So your image displays an old user interface design, or maybe it was taken from a server instance. In the old UI transition options were displayed as buttons at the top along with the assign button. In the new UI that has all changed and each field is editable in the detailed issue view. In any event, OOTB, you cannot add that button to your screen nor cause a modal pop-up to occur. For the pop-up you might look into addon apps.