One of my favourite AdWords Editor new feature (AdWords Editor 6.5) is the ability to expand keywords using the new AdWords keyword expansion feature, embedded in AdWords Editor.
AdWords Editor developpers inserted a new button Keyword Opportunities that is displayed at the top when looking at your keyword list from the "Keywords" tab.
If you can't see it, maybe you use a non-English version and you may not have this button standing there (that's the case for the French version for instance). To solve this, you can use the link at the bottom called "Keyword Opportunities (Beta)". Or you can switch language to English in "Tools - Settings - Locale".
Then you will have a pop window where you can expand your keyword lists by basically using Google AdWords Keyword tool through AdWords Editor. You will have information about search volumes (scaled from 1 to 5) and how important the competition is for these keywords (scaled from 1 to 5 as well). Then, it's up to you to include them or not in ad groups of your choice thanks to the AdWords account navigation tree on the right hand side of the screen.
Then you have the Keyword Multiplier tab (check also this post related to KeyWord Multiplier ) that allows to merge keywords together to build more extended keyword lists (and especially long-tail keyword lists).
This one is my second favourite feature which I will talk about in a second short article.