Lokalize is the localization tool for KDE software and other free and open source software. It is also a general computer-aided translation system (CAT) with which you can translate OpenDocument files (*.odt). Translate-Toolkit is used internally to extract text for translation from .odt to .xliff files and to merge translation back into .odt file.
This button only works with Discover and other AppStream application stores. You can also use your distribution's package manager.