Edit in Builder Button missing

Hi @Ibby Magdalene LA  

Please try below steps: 

1. From Setup, in the Quick Find box, enter Permission Sets, and then select Permission Sets.
2. Create a permission set, and then select System Permissions.
3. Click Edit, choose the Access Drag-and-Drop Content Builder permission, and click Save.
4. If necessary, click Manage Assignments to assign the permission set to users.

Note: Email Template Builder isn’t available for previously created Classic and Lightning email templates.