I have deleted the LDD part database (part library) by mistake. As many of you know, LDD can no longer run in online mode, which means it can't update itself.
Is there any possibility to download the parts from somewhere or recover them somehow?
Here's an archive of the LDD part library for you to download, but I am not certain if it works. Give it a try.
Alternatively, if that link ever breaks down and you have Windows 10 you can right-click on your recycle bin, press open, then right-click on the library file pending deletion and press restore. It will come back.
P.S. If you doubt you will ever use this feature again, you can disable it by right-clicking recycle bin, clicking "properties", and selecting "Don't move files to the Recycle Bin. Remove files immediately when deleted".