Unfortunately, you cannot make your own flyouts at this time through the UI; you can only do it through the API. This blog post talks all about the various types of flyouts:
In the UI, the only type of flyout which can have its content customized is a "Toolbar associated flyout".
So, as a workaround, you could take a toolbar that you are not using otherwise, make the toolbar itself visible (through Tools, Customize, Toolbars), and copy all the buttons you want in your flyout onto that toolbar (through Tools, Customize, Commands). If you want, customize the default buttons OFF of the toolbar if you don't want them also showing up in the flyout. Once you've done that, you can turn the toolbar off. Then go to Tools, Customize, Commands and in the Flyout Toolbars category, drag the image of the toolbar flyout representing that toolbar to the location where you want it.
For instance, you could do this using the Macros toolbar. Put all of your macros at the top and if you wanted to keep the default macro commands on the toolbar, leave those at the bottom since I assume you will use those less often than the actual macros you've customized on there. Then the icon for the flyout will have something that relates to macros. But if you wanted to leave the macro toolbar alone, you could choose another toolbar that has a flyout icon that best works for you to remember what the flyout is for, then use that toolbar, cleaning off all the buttons and only putting your macro buttons on it.
Let me know if any of that is unclear.
Thanks Jim, Oh well.
I will give the workaround a try, I am sure there are a few existing ones I don't use to experiment with.
Thanks for responding so quick.