Question: Does anyone know how I can copy my customizations of XFCE's settings plus its appearance to another machine?

The settings for appearance/design, panels, keyboard shortcuts and geany are not there yet, like at all.

So far I have done:

* copied `~/.config/{autostart,xfce4,Thunar}` (not literally like that)
* logged out and back in, rebooted

Resources:

* <https://forum.xfce.org/viewtopic.php?id=4168>
* <https://askubuntu.com/questions/563382/copy-xfce4-configuration-files-from-one-user-to-another>
* <https://superuser.com/questions/677151/how-can-i-migrate-my-xfce-configuration-and-settings-to-another-system>

Some info, which is true for **both** machines:

```
$ pacman -Qi xfwm4 | grep Version
Version                  : 4.12.4-1

$ uname -r
4.10.5-1-ARCH

```

Answer: 
In addition to what StrangeAttractor has said (the files being in `~/.config/xfce4`, as well as `~/.local/share/xfce4` and `~/.config/Thunar`), there's a caveat: some of the files are overwritten by xfce even if you don't select the "Save session" when logging out. Also, some of the files are loaded in Xfconf and they're not refreshed until you restart.

Because of that, please follow the steps:

* Log out of xfce before copying the files
* Copy the files from the terminal (CTRL-ALT-F1)
* Make sure the proper permissions are set on copied files (they should belong to wanted user; if not, do `chown -R user:group .config/xfce4`)
* Then restart the computer (do not relogin immediately, but restart)

This should do the trick. (Tested on xfce 4.12, xubuntu 18.04)
Make sure to check permissions on the copied files - i.e. do a 

`chown -R user:group /home/user/.config/xfce4`