Although I know how to extend the last system, is it possible to evenly space the bars in the last system rather than just extend the last bar?
Place a "Section End" style barline at the end of the work and set "System Break" in its properties. This will justify the last system better. Some users also like to set the staff to have a hidden (no) ending barline but I find this is usually superfluous and don't bother.
dulfagd, I notice that you're posting a lot of questions here in the Tips and Tricks section of the forum. That's really not its purpose; it's designed for users to share new shortcuts, workarounds, or other interesting ways of using the program that they have come up with. I suggest you read the FAQ (http://www.noteworthysoftware.com/composer/faq/) before posting another question. If you can't find the answer there, or in the help screens of the program, then we'll be happy to answer you here on the forum. But it would be better if "here on the forum" was in the General Discussion section.