Multiple assignees can be assigned to an application. Besides the owner, an assignee also can add other assignees with the following permission:
Then, go through the following steps:
Step 1: Select an application of the client that you want to add assignees.
Step 2: Scroll down and look for the Assignees option.
Step 3: Click on the Add button and select the assignee you want to add.
Step 4: The assignee is added.
Repeat the same process to add more assignees.