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two new ChromeOS flags i have enabled on chromeos 85
Limit Shelf items to active desk
Limits items on the shelf to the ones associated with windows on the active desk – Chrome OS
#ash-limit-shelf-items-to-active-desk
all pinned icons will still show in all virtual desktops < unpinned icons will only show on the desktop you open app/window in
Limit Alt-Tab windows to active desk
Limits the windows listed in Alt-Tab to the ones in the currently active virtual desk – Chrome OS
#ash-limit-alt-tab-to-active-desk