re-link multiple library elements at once back into a file
If you need to relink elements in the Illustrator library you have to link them one at time.. even if it is an instance of the same thing. If illustrator crashes you loose all the links to library elements and I have to go back and link each one at a time. For example I have registration marks all over my artboard, they are all the same, but I have to re-link them back to the file one at a time. It can be time consuming if I have a lot of registration marks. It would be nice if you could hold shift down and select all the missing links in illustrator and then click the element in the Library once to link them back.

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Russ commented
If you need to relink elements in the Illustrator library you have to link them one at time.. even if it is an instance of the same thing. If illustrator crashes you loose all the links to library elements and I have to go back and link each one at a time. For example I have registration marks all over my artboard, they are all the same, but I have to re-link them back to the file one at a time. It can be time consuming if I have a lot of registration marks. It would be nice if you could hold shift down and select all the missing links in illustrator and then click the element in the Library once to link them back.