I need also find a way to get the corresponding .mui and .mun files ..... something like in CheckSysFiles.script
Very possible you already know the info in following two paragraphs, but just in case I will share it here:
I don't know if you are aware many of the Scripts in this project have embeded content, as *.7z, *.exe files, etc., and also some Scripts are hidden, but just in case, I will comment here the procedure I use to extract that files/folders from a hidden Script as CheckSysFiles.script
Just go to \Win10XPE\Projects\Win10XPE\Features\CheckSysFiles.script, open it wit Notepad++ and edit/change Level=0 (hidden) to Level=1 (or any number different to zero), run Win10XPE.exe (that is WinBuilder.exe v082 renamed), and now the Script will not be hidden anymore, in left panel Features section, select the script, select to edit it, open attachments and select x86 and/or x64, select the content in right panel and right click select extract to desktop and you can get the respective CheckSysFiles.exe, after made the previous procedure don't forget to change back the Script Level to = 0, it can be done directly in the builder.
If you were already aware of previous info, please excuse me for boring you, but anyway I consider this info could be useful for some other readers.
For your convenience I attached here CheckSysFiles.7z file Password = alacran
It contains x64 and x86 versions of CheckSysFiles.exe, that you could use to get the corresponding .mui and .mun files.