Studio plugins are loaded from a location specific to each user which has the following structure: C:\Users\[UserID]\AppData\Roaming\SDL\SDL Trados Studio\12\Plugins\Packages.A studio plug can be also recognized by the file type extension which is .sdlplugin. Besides standard plugins that are automatically loaded by Studio you can also build stand alone application that can use Studio API to automate various process or workflows. To run this type of apps you must let them know from where to find the Studio assemblies they require. The most simple way to do that is to copy the application inside Studio installation folder. The main drawback of this approach, as you could already find out, is the fact that you need to be an admin to be able to copy the application (if you install Studio outside of Program Files this is no longer a problem). The other solution, which I recommend, is to use the assembly resolver.

Evzen Polenka As you can see from my above answer the plugins are actually working as you suggested and are loaded from the user profile. Please also keep in mind that this community is about sharing knowledge and helping other community members with their challenges and issues. So please help community fellows by answering their questions in a constructive way from which they can benefit. You can always start your own discussion thread for the topic you consider that is worth discussing within the community.