From 5.3. with Bug 98793 we have functional Mail Merge toolbar, that's improved with Bug 109118.
What's missing is "Show Mail Merge Functions" toolbar button to quickly show/hide Mail Merge toolbar without going to View-Toolbars.
Name is chosen similar to "Show Track Changes Functions".
I'd like to have that button in Standard toolbar, not visible.
I would streamline the configuration and remove the feature of hidden buttons. But as long we have it there is not much to say against a hidden "Show mail merge toolbar" button.
Users can add this button to the toolbar if they wish to from the customization dialog, but there is very limited benefit to have it hidden in the standard toolbar by default.
Gulsah: Have time for this one?