If you want to create a checklist from the text that you copied to the clipboard then you can do it using Smart Checklist add-on!
You might have used this feature in Trello checklists, so now you can do the same in Jira.
Simply copy any multiline text (from spreadsheets, doc, email) and paste to the Smart Checklist Input field. Then press "Enter" and get your checklist items created out of text line.
Note: you can also create checklist items keeping statuses if you use a text formatted with Smart Checklist Markdown support format.