If you have hundreds of instances (all the same) that you want to update in one go, then you will probably want to look at using modules.
It won't help much now if you have already placed all of these elements, unless you replace them with the module.
But once you use modules, you can update the original module file and you will have the option to update each placed instance.
Properly scripted objects will give you more flexibility, as each one can have different settings if you set up the parameters properly.
Otherwise if it is a non-parametric object, you have to modify and save the original object (don not 'save as', as that will become a new object and break the connection).
The all instances of that placed object will update automatically.
You can add hotspots to objects to allow for easier placement in both 2D and 3D.
But when you start getting into objects, you really need to know a little scripting at a minimum.
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