If you load those objects one by one in the Library Manager you will find that they load into the 'Embedded' library and will now be part of the PLN file.
You can even delete the source files (not recommended though) and they will remain (and be usable) in the PLN.
An embedded library object is not available to any other PLN files - however you can export an embedded object from a PLN and then can load it (as embedded or linked (see below) into any other PLN).
If you load the objects as a group (i.e. you load a folder that contains the objects) then they will load as a 'Linked' library.
So long as this linked folder path remains the same then the library will load automatically when you open the PLN.
If the folder path should change for any reason you simply have to link to the new location.
Barry.
One of the forum moderators.
Versions 6.5 to 27
i7-10700 @ 2.9Ghz, 32GB ram, GeForce RTX 2060 (6GB), Windows 10
Lenovo Thinkpad - i7-1270P 2.20 GHz, 32GB RAM, Nvidia T550, Windows 11