I want to create a Tauri app with a dynamic URL and directory.

[jabed-web-dev]

like "tauri-app.exe -url http://localhost:8000"
or "tauri-app.exe -dist path/dir"

"devUrl": "http://localhost:1420",
"frontendDist": "../dist"

[FabianLars]

what's preventing you from doing it?

For the --url option you simply have to set the window's url to that url when you create it.
For the --dist option you'll need to include your own localhost server to serve those files (or use custom protocols) since tauri doesn't have an actual server.