Middle is a macOS app that's made specifically to provide middle click functionality to the Apple Magic Mouse and trackpads.
The app is closed source, but here are the localization files. It's obvious that I've used machines for the translations. If you fix more than a few lines of translations, I will give you a free license for the app (or a refund if you've already purchased it).
Not all text in each file needs to be translated
The current translations for each language have been auto-generated with a lot of text that isn't actually seen by a user in the app. You only need to translate what's seen by the user, and this is in the Master.strings file.
Translations can also be emailed to support@middleclick.app instead of updated via GitHub.
Translations that haven't been touched by a human include:
- Portuguese (Brazil)
Translations for any languages that aren't localized at all are also welcome.
- What is the Viewer and where is it in the app?
The viewer is a visualization of what the app sees from the touch data it obtains. Hold the option key in the menu bar icon menu to see this in the "Debug" menu item.
- Where is the text about panning in 3D modeling applications?
If you select three finger click as the trackpad gesture, this checkbox will appear. It's basically just a way to pan using the trackpad since you can't move it around with mouse click down like an actual mouse.
- What are the "Conflict with macOS three finger drag" text items and where are they in the app?
All of those messages show if you have the three finger drag option set in macOS System Preferences before you set three finger tap/click for trackpad.