There a couple from the Regolith project.

The older is Remontoire, a keybinding viewer.

The newer is Ilia, a Rofi-like tool which can also view and sometimes run keybindings.

But Sway doesn’t make it easy. Sway doesn’t offer an API to see the keybindings so these apps parse a special comment format.

It’s best to think of them as a cheat sheet as it won’t always work to actually to execute the actions.

There is a Wayland-compatible version of Rofi, the package name is 'rofi-wayland' on Fedora. I think it's the same name on Arch and Debian.