I have installed the LibraryManager and LibraryDeveloperToolsSetupBeta on my Win 7 Pro laptop.
After the installation the LibraryManager is working but the LibraryDeveloperTools does not work. Looking around I detected that the LibraryDeveloperTools have been installed in C:\Program Files\ and not in c:\Program Files (x86)\ where the whole Proton suite is placed. I have moved the files from c:\program Files\ to c:\Program Files (x86)\ and YES everything is working.