How to move Photos to new Catalog

Just a warning about deleting many files at the same time. It's one of the slowest commands in the organizer. In many cases, if you select many thousands of files, that will take hours and the process will probably abort for lack of memory/disk space. So, first test how many files you can delete in one batch and delete files progressively when you are not using the computer. If the process aborts, you'll have wasted some time, but you won't lose anything. In the meantime, you can 'hide' files instead of deleting them.

If one of the catalog parts you want to split is very big and you want simply to extract a smaller subcatalog, move the selected files to extract to a new location on the computer (master folder, drive, partition...) after writing metadata to files. Create a new catalog and import from that location. Delete or hide the extracted files from the bigger catalog. You can even recover the keywords structure by saving it in a text file and importing it in the new catalog prior to importing the media files.