Working behind-the-scenes with two themes?

Maybe try a plugin like this one? https://www.ads-software.com/plugins/theme-test-drive/

There’s an article about this here – https://digwp.com/2009/12/develop-themes-behind-the-scenes/
and there are other plugins, but most are very old and probably not up to date.

Personally, I would do all of this on a different server.

Thanks! i’ll look at the article… but yes, i’d definitely prefer to work locally if at all possible! is it?

You can set up a local WordPress install on your own computer using XAMPP or MAMP and work on your new theme at your leisure. Then when the new theme is ready, just upload your theme files to your server and you’ll be good to go.

Thank you. Do you know if I need to install both the core AND developer files for XAMPP or are the core files sufficient?