Rearrange styles in the Microsoft Word Quick Style Gallery
A Workaround

The workaround is to make a separate list somewhere, even on paper (!) or in your head, of what styles you want in the Styles Gallery and then remove everything (or nearly) and reinsert them in your desired order.

HOW TO:

Remove styles until your first choice style is at the front of the list. If necessary, remove all styles and add your first choice to be at the front. Proceed through your list, adding styles into the list in the order you desire.

Since you are identifying your top 6 or 10 styles, reinserting them into the list manually is not an onerous task.

This works if you only use your own defined styles. However, if you use some of the built-in styles, those may get bumped to the front of the list anyway. For instance, you usually only use Title once per document, so it's not really a style you might want in your "Top 5" list, unless you need to be reminded to always give your document a title. But if you add it to the Quick Styles Gallery, it will always be near the front of the list.

If the previous post is true, and it appears to be so, that it is "currently not possible" to change the priority level, that's very sad and another way that shows that Microsoft is not interested in Word being useful for professional writers and designers. (Changing the priority may be possible through editing the XML code, according to one post, but many people could not make that method work for them.)

This is a useful tool and it really should be simpler, if Word is to be a truly professional tool. Making the Style Gallery order drag-n-drop would be the "user friendly" thing to do. But since Word has far more amateur customers than professional, don't hold your breath for it being done "right".