Hi,
I have added the following edit to my post above re how to edit an MSM button....

[ UPDATE 7-23-2010 - The info in the doc below reflects the state of affairs as of MSM beta 1 (and 2). This is an area of internal implementation that is going to get a pretty major redesign. The methods for modifying an MSM button are very likely to change significantly within the the next couple of weeks. ]

The planned changes in this area are a key reason I don't advise people to modify MSM in early beta. I hate to see people have to do work over again - but that's the trade off if you choose to explore code modification methods at this time.

Frankly, the current beta makes it very hard to make mods that "stick" - an MSM beta install will overwrite most mods.  In fact, MSM Beta 1-2 is so zealous about this that it is hard to add a button to the user exts page.  It was known that this was the case when we started the beta.

In case you are wondering, the tension is between:
1) The need of the software vendor to be able to check user bug reports against known configurations of a product, and the need to push code updates to users.
2) support for user customizations.

MSM uses two concepts:
a) MSM "master files" (things that MSM installs and always updates when an install occurs) and
b) User modified **copies** of master files.

Effectively, MSM Beta 1-2, has the master concepts implemented, but not much of the user modified copy concepts.
The extent to which Mach allows users to customize (synonyms: "fiddle", "break"  ) makes this no small challenge.

I'm working on this area now - but it will take a while to get the desired support for user mods implemented.

Dave