Open in app button for itch.io
A downloadable userscript
This is a userscript that adds an "Open in app" button on all itch.io game and user pages.
For the button to work, you need to get install the itch app first: https://itch.io/app
Then you need a browser extension that lets you install userscripts. I recommend using Tampermonkey for Chrome:
You can grab the script from its GreasyFork page: