The WIKI already has just this: http://lmwcs.com/rptools/wiki/Category:Cookbook
This is basic "HOW do i?" for common things such as modify health bars, etc.
That's a good start. However, I didn't notice that, because it's in no way referenced on the main page of the Wiki. If I get a chance, I may look to fix that if someone doesn't beat me to it.
If you are looking at frameworks, those are stored in the user creations forums and it's as simple as downloading a campaign and reading the docs(harder if you want to merge with an existing campaign). Unfortunately, there are only 3-4 game systems represented there... add another one!
When I get my basic framework done for WFRP, I'll be sure to share it. Sadly, the ones I found supposedly already done don't load up - as far as I can tell, they seem to be corrupted (aren't campaign files just zipped? - Winzip reports them as invalid files).
Basically, the more complex a macro gets, the more it is based on a series of assumptions, settings, and properties that the macro designer created in order to support the macro's functions. There are no standard property libraries (though some people are moving in that direction) and macro depend heavily on the properties that they work with, so the more complicated and game-specific they get, the less reusable they are.
Understood. But the larger the library gets, the more likely there will be one to fit someone's specific needs. It's also often easier to start with someone else's code, and modify it to fit your needs than write from scratch. And with a good repository, hopefully those modifying things they download will be encouraged to upload their modifications, thus making the library of functions even bigger.
I do realize I'm being wishful when I ask for MT to automate the installing of macros from an online repository. But I do realistically think there are ways to make things easier. One is central place to post all macros in an organized, easy to search and central location. The Code Cookbook on the wiki is a good start to this.
Another idea would be Macro writer "wizards" for some of the most common functions. These wouldn't necessarily have to be within MT itself, either. FREX, a common Macro for people is going to be an Attack roll. A "wizard" could ask a user a series of questions like "What dice to use?" and "What token property represents the attack bonus?" and spit out a code snippet.
These are all just ideas.