How to mass-remove Items from the Smart Library (But not Permanently) ?
tl/dr I lost my HDD and now my Smart Content Library is full of Hundreds of "File does not Exist" Items.
How do I mass delete Items from my Smart Content Library without having to manually right Click and remove each one Individually?
I don't want them to be turned invisible, for when I am able to download and instal them all later again. Just for the Time being.

Comments
If what you mean by "file does not exist" is a white thumbnail with an exlamation mark in Smart Content, just go to Content Library > Products > L > LOCAL USER.
Click an item and Ctrl + A to select all items, right-click > Remove Orphaned References...
If you have multi-pages of the items, you need to do the above operation for a couple of times ~~