To move the file just hold the [Alt] key when pressing K or clicking the Keep/Copy menu.
The keep/copy destination folder is an absolute path. If your pictures are in, say, C:\Pictures you can set it to C:\Pictures\Selection but (currently) not to ".\Selection", i.e. relative to the folder containing the image being viewed, although this is a good idea and might be added in a future version.
The File Utilities plug-in (F key) can copy/move files to relative locations, however, and can act on files according to numerous criteria (not only XMP rating). You could use another flag, for example mark the keepers for publishing using the P key, then build a "Move" rule using that flag as condition and have the batch processor move all marked files at once for you. The drawback is that the Publish flag is transient, i.e. it does not persist across sessions, so you'd have to run the batch job before exiting the program.
Another way would be to use the XMP rating system and let the program create sidecars next to your raw files, then make two rules for the batch processor: the first rule would
copy the files to the ".\Selection" relative subfolder and the second rule would delete the original file just copied and the XMP sidecar, leaving no clutter behind. In fact you can create as many rules as needed to perform almost anything with the files, you could for example add another rule in between the above two to copy the keepers to a second location, say on another drive for backup purpose, and add yet another rule to delete all unrated files, or only those with a rating below a certain value that you chose. You can then save this set of rules and give it a name, making it easy to recall the entire task at a later time.
The batch processor should be able to cope with nearly all workflows one way or another. I warmly recommend that you spend some time exploring the possibilities as part of your evaluation, perhaps starting from the
turorial.