Changing plugin code

It would take some doing as the tabs are taxonomy terms leading to multiple posts, not individual post titles. How would the script know what content to open? It’s maybe possible to code a custom page that does what you want, you’d be mainly just using the theme’s CSS for appearance. To do major coding like this, you should create a child theme. Many themes like this are already child themes of a common framework, so it’s not possible to make your own child theme that protects your code from updates.

You could setup the theme to never update, but then you are open to security vulnerabilities that may be discovered. Not a good option.