When creating a project, or a 3D scene more often than not you want to be able to handle properties on multiple objects at once, for quite a long time that was very difficult or maybe impossible if you didn’t have the python coding knowledge required.
These days blender is becoming more and more easy to use and it’s keeping in mind the rest of us who can’t code or just don’t want to code things that we feel should be a default options.
Anyways, i’m very grateful that they have made a few options available for us like these two examples… so first there was “Copy to selected” where you can select many objects, click on a property, attribute or option and then right click on it select Copy To Selected (if available) and it would apply the same to other objects, like locking transforms, etc.
And now a days we have the Alt+Click combination, which i believe it should work just with click, because when you want to do things to just one object, your reflex is to select that object and do things to it, and if you want to do it to multiple object the same principle applies…
anyways, the second one just consists of selecting multiple objects and holding alt when you want to apply some option or even drag a slider… you poeple who like my use “emulate 3 button mouse” for your tablet to work more comfortably are out of luck, it just wont work.
The Adventures of LollypopMan 
Actually if you hold the left mouse button and then hold alt, you can do the alt click.
Though I can’t see any practical enough reasons to do that or disable 3-button mouse over doing it manually (they would take more effort than they’re worth).
However ctrl+alt+mouse wheel will drag the slider values in multiple objects, .
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