sphilips,
Yes you can export your shortcuts with some rules and exceptions. Here is what I have found with just a bit of experimenting.
First your shortcuts are stored in your Work Environment profile. You will need to go to Options>Work Environment>Work Environment. At the top of the list on the left, click Work Environment Profiles. Select the one you primarily use (this profile should have your custom shortcuts applied) and click export to save a profile package (I saved mine to a USB drive). Plug the USB drive into your Windows machine and via the Options>Work Environment> Work Environment>Work Environment Profiles, import the profile. Note: just look for the directory the profile is stored on. For instance I stored my custom profile in the root directory of my thumb drive so I just browsed for F:\ and ArchiCAD found the available profiles in the directory. If you use multiple profiles, then repeat the process.
Note: Since MAC and Windows keyboards are different COMMAND(MAC)=CTRL(WIN); ALT/OPTION(MAC)=ALT(WIN) and any shortcuts using the CTRL button on the MAC will not appear in your Windows environment sorry to say. You will have to re-map those.
This is as much as I know from a little bit of experimenting, maybe others know more. HTH