When manipulating a group of captions in Premiere Pro, the application is glacially slow.
We have completely redesigned the captioning workflow in Premiere Pro version 15.0. You will see many dramatic workflow improvements. Please update to the latest version.
Learn all about the new captions workflow here: https://helpx.adobe.com/premiere-pro/user-guide.html/premiere-pro/using/working-with-captions.ug.html
Clint Porter commented
Still a problem.