Using the title bar on multiple windows

[powerlego]

Hi, I have a project that I am working on that creates child windows, e.g. a preferences window. How do I utilize the custom title bar in this case? The documentation isn't clear on how to utilize this on multiple windows. I have tried doing a similar setup to the main window, but when calling the setupTitlebar function for the other window, I get an error saying:
Error: Attempted to register a second handler for 'request-application-menu'.

[powerlego]

I have figured out my issue, I forgot to disable sandboxing on my other window, which caused the module to not load.