The GUI files can be found inside the .big archives originally supplied by EA SPORTS (assetCmn.big, assets.big and  gui.big) but also directly in the appropriate subfolder of the gui folder itself, for example "data/gui/assetCmn/lglogos" and so on. CM10 searches in the folder first, then it looks in the archives. When saving you can choose whether to save in the archives or directly in the folder by pre-setting an option in the Options menu.

CM manages the files saved in the archive and the files saved directly in a folder differently – the first are kept in memory, and saved only when you save your editing work by clicking on the Save menu, the latter are instead saved immediately as soon as you perform an operation. The big files are not saved as soon as you make a change because these files are very large and saving them could take a long time. If you would like to protect the GUI files from accidental editing you can uselect the option "Allow GUI Saving "in the Options Menu.