How to have different screen for different issue types with single screen scheme Default Screen Scheme ?

[Ravichellam Ponnusamy]

I use a single default screen scheme for all my project. But for one project alone I have an issue which needs only some customs fields to be shown on that issue.But that those customs fields are required for all others projects. 

[Nic Brough [Adaptavist]]

We'll keep this simple at first:

Create a new screen for your issue type.  A screen is a list of fields you want to show.

Create a new "screen scheme" - this lets you say "for Create, use screen X, for View, screen Y, and for Edit, screen Z".  Select your new screen for all three for now

Create a new "issue type screen scheme" - this links issue types with screen schemes.  In here, tell it that you want to use the defaults for everything to start with, but then add your issue type as an exception, selecting your new screen scheme.
Associate the new issue type screen scheme with the porject.

[Ignacio Pulgar Martín]

Have a look at the documentation:

https://confluence.atlassian.com/jiracloud/configuring-fields-and-screens-735940719.html

The diagram is specially useful to understand how it works.