When the Multitool has finished Unpacking the game files, there are still files that can't be worked with directly, with extensions like .lsf, .lsb, or .loca. Fortunately, the Multitool can decompress these files into editable .lsx and .xml files. To do this,go to the menubar and click on Utilities -> File Operations -> Decompress Files. You'll see this dialog prompt open. Hit Yes, and wait for it to finish processing the unpacked files for decompression.

Once it's complete, every decompressed file will be editable, and have a filename that looks like Filename.lsf.lsx, Filename.loca.xml, or similar. The text after the first . indicates the original extension, while the text after the second . indicates the new decompressed extension. This filename structure is especially important, as when you go to package a mod, any files with this filename structure will be converted to their original extension.