The next months I will have to travel a lot.
I have a few projects to edit as well. All the footage is on a RAID, which of course I can't take with me while traveling.
I heard that FCP has a function to be able to edit in low-res on a Macbook Pro, while keeping the original files on the RAID in the studio?
I've been searching posts and reading the manual. But I seem to overlook how to use this possible great feature?

Ken Stone is your friend if you use FCP.

http://www.lafcpug.org/tutorials/basic_low_res_capture.html

Suggestion: Not sure how big your project is but you could buy a portable firewire RAID drive. OWC drives from Macsales.com have some good deals and can go upto 2TB. That way your basically editing online and you can see any possible inherent problems with the footage or begin color correcting. Also they have been fast enough to allow for multi-clip editing and quick enough for intense rendering. Personally I use the OWC drives and just pack them on my carry-on.