For browsing the bundle and adding things I recommend browsing on the bundle’s page right now, as there are the most filtering options: https://itch.io/b/1316/bundle-for-ukraine
Once you’ve clicked into a game there will be a button on the top to download the game which will automatically make it appear in the app ready for download assuming you are already inside the app.
I do not recommend adding everything either manually or with a script. We intentionally designed the bundle this way and you’re going to have a degraded user experience using a third party script to flood your account with games. Any updates to bundle game browsing and discovery will be built around the fact that not every game is inserted directly into your library initially.