In the backend of Pimcore, there is an area for managing documents, assets, and objects. This is located on the left side of the browser window. Only one of these sections can be open at a time. Using the ">>" buttons, you can move a section to the right edge of the browser window (and from there move it back to the left using the "<<" button). In this way, Pimcore allows you to open several sections at the same time (one on the left and one on the right) or to change the order of the tabs.