You can add multiple versions of the same tool with different settings to a shelf. For example, you can add a Sculpt Surfaces Tool with the Push option selected and another Sculpt Surfaces Tool with the Pull operation selected. This only works with tools, not regular menu items (actions).
For example, you could modify the parameters of the NURBS sphere tool by selecting the option box and changing the settings in the NURBS sphere window. You can then save the tool settings as a shelf button by holding + and clicking the menu item. The shelf button is saved with the settings currently specified in the settings window.
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