In 2009 or 2010, you can use the search edit box at the top of the Application menu (which deploys when you click on the big red "A" in the upper right corner - just do not double click, as that closes the application!) to find the location of a given command. In 2009, it appears to be limited to the commands on the pulldown menus, for ACA at least.
In 2009, if you have the Design pulldown activated, the command can be accessed via that pulldown: Design > Walls > Insert Endcap Style as Polyline....
In 2010, the endcap-related tools are on the Wall contextual ribbon tab, on the Endcap panel, but AecWallEndcap is not one of them. You will have to type the command, create your own customization to run the command or learn how to use edit-in-place. If you have not tried edit-in-place in a recent version, I highly recommend you try. When it was first introduced, I had a hard time getting it to do what I wanted and generally stuck to creating polylines. In 2009 and 2010, it is greatly improved - to the point where it is actually quite usable.
http://architects-desktop.blogspot.com/2008/02/autocad-architecture-2009-part-2.html
David Koch
AutoCAD Architecture and Revit User
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