I'm trying to answer from memory, and am not at home to double-check before sending this answer, but:
You can only move samples around in the same .esx file. By that I mean, you can't open 2 .esx files (A.esx and B.esx), then copy a sample from A.esx into B.esx.
You can, however, move/copy any sample in A.esx, and move it to another location in A.esx.
I also do some checking so that the same exact sample cannot be entered into the same .esx file twice. That is to prevent "duplicate" data (and to save space).
If you really need to get samples from A.esx into B.esx, you can use the "sample export" functionality:
- Open A.esx
- Export all the samples to a directory on your computer (there's a menu item, or button you can click that let's you export samples). You can also set the "export name" in a preferences menu.
- Now that you have all the samples exported, you can open B.esx
- Now drag-and-drop (or use "open" from the menu) the samples you just exported into the B.esx file. You can arrange them however you like once they are imported into the file.
Not sure if this makes sense, or helps you out at all. Let me know if you need clarification, or if there's anything else I can do to help.