From the latest patch notes: " * Shift click in resources panel allows you to select all idle workers or all workers in the clicked resource."
I tried this and couldn’t get this to work at all with a fresh install and no mods ever subbed/dormant etc.
It has also been reported on reddit here: "Shift click in resources panel allows you to select all idle workers or all workers in the clicked resource. " : aoe4 (reddit.com)
Thank you.