Currently Tweak Utility uses Windows Forms as it's UI Framework, not new but functional. You can grab the Strings.RESX file from here, and edit it, a text editor (or Visual Studio if you can't read XML) should be enough. If done, create an issue or contact Craftplacer. If accepted, the localization will be shipped in the next version of Tweak Utility alongside with a mention in the credits as translator.
& are used in Windows Forms to give UI controls a keyboard shortcut, so if a control is labeled as "Being Tr__a__nslatable", you can activate/click it by pressing Alt+A.