Double-click on the mid-point of the right edge of the panel.
On Mac, the Source Browser can be hidden, displayed, or adjusted in the following way:
Folders: is divided into Favorites (favorite folders on macOS), Devices (drives and folders), and Shared (storage and folders shared with macOS).
Recent Searches: displays a list of recent searches.
Search for images: search input field, search results, and the Index a folder option.
On Mac, it is divided into the following sections:
Projects: displays a tree hierarchy of projects and project groups.
Folders: Displays a tree hierarchy of the files and folders as they are on your computer storage.
Search for images: search input field, search results, recent searches, and the Index a folder option.
On PC the Source Browser is divided into these sections: The Source Browser, available in the PhotoLibrary tab, lets you explore the folders on your storage devices as well as the projects stored in your DxO PhotoLab database. Light | Dark Managing & searching images The Source Browser
Using a virtual copy as a reference image.
Creating a project from a selection of images.
Creating an empty project or project group.
Selection status, star ratings and color labels.
Displaying attributes and comparison modes.
Sorting and selecting the best images in Fullscreen mode (Viewer).
Filtering and searching for marked images.
Searching, collecting, and viewing images with IPTC metadata.
Searching for and collating images using keywords.