Is there any way to rotate a magic trackpad?
You have three options that I'm aware of, but depending on the version of macOS you're running, probably only one of them is a real chance of doing exactly what you want.

In summary:


Use Terminal commands to rotate the trackpad orientation. However, the commands I'm aware of only work to rotate it 180° instead of 90°. It also doesn't work for macOS Sierra or macOS High Sierra. If you're running an earlier version of macOS and rotating 180° is an option for you, then see details below for Terminal commands.
Try using MagicPrefs, however this is now on its last legs as an option. It's worked brilliantly for many users for a long time, but for various reasons is no longer maintained
Try using BetterTouchTool. This is probably your best bet. You can install it for free for 45 days to test how well it meets your needs.


Terminal commands

If you decide that rotating your trackpad 180° will meet your needs, and assuming you're running an older version of macOS, then follow these steps:


Launch Terminal (usually found in Applications > Utilities)
Enter the following command (or copy and paste it):

sudo sudo defaults write com.apple.MultitouchSupport ForceAutoOrientation YES
Press Enter
Enter the following command (or copy and paste it):

sudo defaults write com.apple.trackpad.orientation TrackpadOrientationMode 1
Press Enter


Once you've entered both commands you should be able to just turn Bluetooth off and then on again to activate the change in orientation.