All I want to do is take large videos, cut them up into small clips, and then reorder those clips into a new video. Yet this seems completely impossible to do with Final Cut Pro X… it can't be impossible because this must be a common need but it won't let me copy the cut clips into the media library and if I can't do that how can I do this? Why is this so hard to do?
The clips you cut in your timeline can’t be copied into the media pool because technically these aren’t individual clips yet. Just references to the original media. You can rearrange these easily in your timeline. Just drag and drop clips in your timeline. Everything will move around the clip you change position.
Calm down. Final Cut Pro X is a software for professionals and as such requires a certain investment of time until you can work with it. If you are not willing to do this you should look for a simpler tool.
Yes, of course it's possible to do what you want, but to me it sounds like you don't know the basics of how to operate the software. To get you started, these videos might help you:
When you import clips into Final Cut Pro and make a project, they should all show up in that project. If you want to put specific clips in the timeline, then you need to select the specific part in the window that includes all your imported media. None of the imported media will go away if you do this. Once you import the media, it doesn't matter how much you cut it up when editing, the media will still be there.
It's certainly possible to drag all of your clips to the timeline, then chop out the parts you don't want, and then drag-and-drop the remaining pieces into the order you want. I used to do that with the old-school version of FCP (prior to FCPX), and it still works. (In fact, as you do this, it closes gaps where you delete parts of clips, which is very convenient.)
Or, you can play the clips in the bin using J/K/L to control playback, I/O to mark in and out points, and E to take that part of the clip and throw it into the timeline at the end. So you could hop around in the clips in the bin, throwing pieces you want into a rough cut in the timeline without ever touching the timeline.
Or, you can play through the clips in the bin and use markers to remind you where you're hearing/seeing things you really want to use, then go back and do the I/O/E thing to throw them the timeline. (You can be a little loose and fast with your I/O since you can always expand your clips in the timeline to reveal parts you missed with your I or O.
And you have options other than E to put pieces of clips in the timeline at places other than the end. (And you can drag-n-drop highlighted pieces of clips into the timeline.) For example W will insert the currently selected piece of a clip into the timeline at the current playhead or if you move your cursor down into the timeline it creates a red line where the insertion will occur. You could literally jump to 5 places in your timeline and insert your clip 5 times in about a second if you wanted to.
If you're envisioning cutting clips up and arranging them in the bin, FCPX doesn't work that way as far as I can tell. If you're troubled by the pieces of clips sliding around in the timeline to close gaps, that's the storyline concept of FCPX: you have a main storyline that closes gaps and to which you link supporting elements, above, that move with the part of the storyline they're attached to but that do not close gaps when edited/deleted.
FCPX is different from most editors and from prior versions of FCP. It's relatively affordable, but it's very much for professionals who expect to use keyboard shortcuts, want to work super-efficiently, and don't mind learning the foundational concepts that FCPX is designed around.