Here's a rather lengthy explanation, which I hope is helpful.
*Galleries*
Building blocks are organized into galleries such as AutoText, Quick Parts
and Page Numbers; there are 35 built-in galleries; you cannot create new
galleries (15 built-in, 15 more with “custom†preceding name of each built-in
gallery (for example, Custom AutoText) and 5 named Custom 1 to Custom 5)
*Categories*
Galleries in turn can be organized into categories; by default the only
category is General; you can add as many categories to a given gallery as
you'd like
*Quick Parts Gallery and Categories*
When you click Quick Parts on the Insert tab, in the Text group, you will
see the building blocks in the Quick Parts gallery organized alphabetically
by category and within categories alphabetically
If you organize AutoText entries into categories, I would think it would be
easier to find them in the Quick Parts gallery so long as you do not have
many other building blocks that you have classified as Quick Parts. I do not
use this approach.
*AutoText Gallery and Categories*
Personally I prefer to classify AutoText entries in the AutoText gallery and
create categories within the AutoText gallery; the advantage of this approach
is that the Quick Parts gallery is reserved for commonly-used building
blocks other than AutoText. But how do you display them quickly? You need to
add the AutoText button to the Quick Access Toolbar.
*Adding the AutoText button to the Quick Access Toolbar*
Either click Customize Quick Access Toolbar triangle on the right end of the
Quick Access Toolbar to display the Quick Access Toolbar Customize menu and
click More Commands to display the customization options (the "command well")
-or-
Click the Microsoft Office Button to display the Office menu and click Word
Options to display the Word Options dialog box; click Customize to display
the customization options
Then:
In the Choose commands from drop-down list box, select All commands
Scroll down and select the desired command (AutoText)
Choose where the customization is saved (by default in Building Blocks.dotx)
Click Add
Click OK
When you click the AutoText button, you’ll see AutoText entries in the
AutoText gallery organized by category; the categories are in alphabetical
order and the AutoText entries in each category are sorted alphabetically by
name; no other building blocks are displayed
*Naming AutoText entries and using the stripped down AutoComplete feature*
Even though the AutoComplete feature has been severely limited as a result
of integrating AutoText entries into building blocks, it is still very
useful. But to be able to use the AutoComplete feature efficiently, the
AutoText entries must be named with unique names (preferably combining
letters and at least one number in the 1st 4 characters of the name). As soon
as the characters you enter are unique, you press F3 and the AutoText entry
is inserted. The uniqueness of the name has to apply to all building blocks,
not just those within a given gallery or category with a gallery. Unless you
have hundreds of AutoText entries, I find this is by far the easiest way to
insert AutoText entries.