I tried the above instructions in the Lukas Viewer, and tried each of the 4 "save" buttons at the bottom of the window but none of them seemed to work; the only one which appeared to be a "save" presented a "save as" window, which I saved to the SD card folder on my hard drive (note: not the actual SD card), however when I went to re-open the settings window, the "language" button had reverted to the original (first) button rather than the one at the top of the second row. It appears this "language" setting doesn't seem to want to work, as all other changes made in that tab and other tabs always seems to be kept (remains the same when the settings window is re-opened, and not revert to default like the language option does).
It's possible it's not correctly saving it because the SD card isn't in the laptop; I'll try it again next time directly saving to the SD card instead of a backup folder I have on the laptop hard drive.