To find Catalog Management, navigate to Catalog>Catalog Management. 

Catalog Management helps with tasks such as moving, adding, and deleting catalogs as well as allowing you to control the size of preview images to save space.
Use the triangles to find more options next to each catalog.

The Catalog Management dialog also indicates which catalogs need maintenance, for instance after Photo Mechanic Plus has been upgraded with a newer version of the catalog.

Maintenance Options

Forget: The Forget button does not delete a catalog but removes it from the list of available catalogs as if Photo Mechanic has forgotten it is there. Use this to move catalogs to another computer or location. Use Reintegrate Forgotten Catalog to restore.
Rename: Use this to rename a catalog. 

Delete: Use this to delete a catalog - just the catalog, index, and preview images. The original images will remain.
Calculate Catalog Folder Size: See how much disk space is being used by your catalog and stored proxy preview images.
Generate preview & thumbnail proxy images: Check if you want to see previews of images in catalog contact sheets without having to generate new proxies from the original images each time. This is faster but uses more disk space. 

Proxy Storage:

By default, this option will be set to “Store with catalog”, and Photo Mechanic Plus will store the proxies it creates in a folder called Proxies within the Location path of each Catalog.

Before this setting can be changed, the new location to store the proxies must be set in Catalog Preferences

Once a location is set in Catalog Preferences, return to the Catalog Management window, and click on the dropdown under Proxy Storage, and then choose your preferred option between Store with Catalog and Use External Storage.

  • Changing this setting requires moving all of the proxy files from their current location to a new one. The duration of this operation will depend on the number of proxies, how large the files are, and the speed of the drives the the source and destination directories are on. You will be prompted to confirm your choice before Photo Mechanic Plus begins the operation

Preview size: Use this to control the maximum size of proxy preview images indexed inside your catalog. If your catalog is taking up too much space, but you still want to see thumbnails, decrease the size of the preview images.
Maintenance: This triangle pulls down database maintenance options. The options are:
Optimize SQL Query Planning: This is recommended after adding or removing a large number of documents to or from the catalog.
Reintegrate Forgotten Catalog: Use this to "unforget" a catalog.
Re-index Catalog: This is rarely needed. See this article on how to use it.
New Catalog: Create a new catalog.
Locate Existing Catalog... Point to a catalog that has moved.

Further reading on tasks that use Catalog Management: