How do I make a QR code menu for my restaurant without a separate QR code menu generator?

It is built in. Add your tables under Settings → Tables & QR ordering and each one gets its own scan link the moment it exists. Press QR design & print pack, pick colours, a caption and a card style, and download a ZIP with a PNG and an SVG per table plus an A4 PDF. A guest who scans the card sees your menu with the table already known and orders without typing an address. A QR code menu generator on its own gives you a picture; this gives you the picture and the ordering behind it. The Dine-in, QR & group orders tab in the docs has a guide on printing the cards.