Customize

Most commands can be added to the Quick Access Toolbar when using this dialog box
This allows you to make multiple changes to the commands

To add a command just find it and press Add

Adding and Removing Commands

The quickest way to add (or remove) a command from this toolbar is to
Display the Customise Quick Access Toolbar menu and tick and untick certain commands
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or right click any ribbon command on any tab and select "Add to Quick Access Toolbar".
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Customizing the Toolbar

Display the Customise Quick Access Toolbar menu and select "More Commands"
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or right click on any command and select "Customize Quick Access Toolbar"
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or from the Options dialog box by selecting (File > Options)(Quick Access Toolbar)
In Excel 2007 this is (Office > Excel)(Customise tab)
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All Commands

If you cannot find the command under Popular Commands, you can browse more commands, including Macros and those which are not included in the Ribbon, among many others.

They appear in the Excel.qat as

<mso:sharedControls> 
<mso : control idQ="x2:UpdatePalette" visible:="true" /> 
</mso : sharedControls 

If you are experiencing problems with your QAT losing your commands a permanent fix would be to create a very simple Excel add-in which contains the necessary QAT ribbon customisation

Resetting the Toolbar

Reset only Quick Access Toolbar
Reset all customisations
can you email and share the QAT file

Changing the Scope

By default any changes made to the Quick Access Toolbar will be saved as a user preference and will be displayed whenever Excel is open
It is also possible though only to make changes for a particular workbook
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Using Customization Files

These can be imported and exported
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Maximum Number of Commands

There is not a maximum that can be added although the size of your screen will control how many are visible at any one time.

Can't rename any of the commands
You can only display icons and not icons and labels

Important

Only commands can be added to the Quick Access Toolbar. The contents of most lists, such as indent and spacing values and individual styles, which also appear on the Ribbon, cannot be added to the Quick Access Toolbar.
There is no easy icon editing capability