Hi Saikrishna,
In classic UI, while promoting launch, you would notice an extra option "Add To Workflow Package".See detailed steps as below:
To promote pages, perform the following steps while editing the launch page that you want to promote:
On the Page tab in Sidekick, click Promote Launch .
Specify the pages to promote:
(Default) To promote only the current page, select Promote Page Changes To Production Version .
To also promote the child pages of the curent page, select Include Sub Pages .
To promote all pages in the launch, select Promote Full Launch To Production Version .
To add the production pages to a workflow package, select Add To Workflow Package and then select the workflow package.
Click Promote
https://docs.adobe.com/content/help/en/experience-manager-64/classic-ui/launches/classic-launches-pr...
Thanks,
Vaishali