You can convert BSP brushes into static meshes, but you can't do it with anything else. What you are probably looking for are prefabs; select numerous meshes, right click and then "create new prefab" it will ask you for a package. You can then move the assets around as a whole and if you want to turn them back into normal assets, right click and convert to normal actors; but even tho you do you can still reuse it from the prefab saved in the package. About the packages, if you want you can create a new one by typing a new name in or select the internal level package. Thought you can not use it in other levels. So if your asset is stored in the internal package of a level called "mall" you can't use it in the other (sub-or persistent doesn't matter) levels; I told you this. Also I'm telling you this because it's way better than modding existing Mirror's Edge upk files, it's faster and good for a single map.
clicking on ".rsvp" adds class "open" on ".overlay"
clicking on ".close-overlay" removes class "open" on ".overlay"
clicking on ".rsvp, .overlay-m-open, .overlay-m-open-en, .open-bs-modal" adds class "no-scroll" on "html"
clicking on ".close-overlay, .overlay-m-close, .close" removes class "no-scroll" on "html"
clicking on ".open-menuprofile" adds class "open-mpro" on ".menumi"
clicking on ".close-menuprofile" removes class "open-mpro" on ".menumi"
clicking on ".overlay-m-open" adds class "overlay-m-visible" on ".overlay-m"
clicking on ".overlay-m-open-en" adds class "overlay-m-visible" on ".overlay-m-en"
clicking on ".overlay-m-close" removes class "overlay-m-visible" on ".overlay-m, .overlay-m-en"