You are copying the clipboard to the named clipboard “Default Clipboard”, then you are applying styles to the named clipboard “Default Clipboard”, and then you are ignoring it completely and pasting in the current clipboard.
Instead, use:
- Type the ⌘C Keystroke
- Apply Style to System Clipboard
- Type the ⌘V Keystroke
- Delete Past Clipboard 0
Note that there may well be timing issues with that - if the application takes too long with processing the ⌘C, then the Apply Style action will work on the wrong clipboard. Also, if the application takes too long processing the ⌘V, then the clipboard may already be deleted by the time it gets around to it, resulting in the original clipboard being pasted.
And finally, there may always be clipboard caching problems whenever you change the clipboard in an application.