How to add new websection? and how to showcase the some other issues in that section?

[Kumaravel Chandrasekar]

I would like to add a new web section under the description. In that websection need to add a custom field and showcase some other issues (issue key, summary & status)

[Peter-Dave Sheehan]

Enable the "fragment locator" (see the link in the fragment maintenance screen)  to see where elements can be injected. In this case, this reference may help: https://developer.atlassian.com/server/jira/platform/issue-view-ui-locations/

I found that a weight of 200 will place the websection just before the description and a weight of 201 will put it after.

As far as what you put in that web section, that's up to you. You just have a to build some HTML. 

I'd recommend using the groovy xml markup builder.

Then use the various jira java api fetch the information about the current issue that you want to display.

You are entirely in charge of the styling. But you can leverage classes present in the AUI