Qubes/Tails with persistent usb drive

I am trying to create a Tails setup inside QubesOS. It’s not about security/privacy. I think it’s a practical way for Tails documentation (e.g. screenshots).

I already have a running Tails VM by following this guide:

I am also aware of the “Tails Troubleshooting guide”:

However, I don’t understand how to create a persistent storage for Tails. I do not have one at hand. I would like to create a new one. Either using part of my main hard drive or adding a USB stick.

Please help me out. Thanks.