Resize images as a group?

I have a document with a bunch of images on it and I want to resize them all at once, so that they are equal dimensionally.
Since I can’t seem to command-click to select more than one at once, or click and drag, I’m wondering if there is another way?

Cheers.

I do not know any feature in LibreOffice that fulfills your wish to convert multiple images at the same time in size.
Suitable for this purpose are graphics programs which can perform a stubble processing, e.g. Gimp or IrvanView. But you can not do this within LibreOffice. You should have all the pictures in a folder and then start a batch process. Then you can integrate the converted images into LibreOffice. But in the end it is not a question that specifically concerns LibreOffice.