It works and does really load all tabs. Some other Tab-Addons dont do this. Very strange ...
But as already mentioned here: it should be in the tab-menu-context not on the page. Did not find it there.
And: very helpful would be an option "Reload all tabs to the right". So i can work with my last session in a more efficient way (if i have 60-80 tabs still to check), only opening 20 at a time.