Hi,
our developers have just tried it in our local installation and it works fine!
Maybe some plugins you have installed (or your theme) are causing this issue.
Please, try to deactivate all plugins, leaving only WooCommerce and YITH WooCommerce Custom Order Status active, and see if the problem is solved. If so, try to activate them again, one by one, to see which one causes the issue.
If the problem isn’t caused by a plugin, try to activate the default theme Twenty Sixteen and see if you have the same issue.
Also, if you have customized some files in your theme, please try with a fresh installation without any customization.
Please try this solution and let us know what’s the result.
Also there is magic buttons to fast changing without images (not so usable as in idea)
Unfortunately this feature is not included in this version of the plugin, but the premium version supports it (custom icon or text). If you need more information about it, please, do not hesitate to contact us on yithemes.com, our pre-sales operators will be able to help you.
Best Regards