There are two ways to clone multiple issues at once:
1. Bulk Clone using the Jira issue search.
Filter the issues you want to Bulk Clone by using Jira Issue Search.
Click the Bulk Clone button.
Configure and create your Bulk Clone.
2. Bulk Clone from the Deep Clone navigation
New navigation: Next to the “Create” button, select Apps>Deep Clone / Old navigation: Click Deep Clone in your Jira navigation
Click Bulk Clone in the Jira navigation on the left.
Filter for all issues you want to bulk clone by JQL, a favorite filter or project
Configure and create your Bulk Clone
If the Bulk Clone button is not visible, expand the menu by clicking the expand arrow.