From BlenderWiki
Tool shelf
This panel contain sort of bookmarks of commands you wanna do often in the selected mode.
(to be written)
Brush
Active Brush Index
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Brush Browser
(to be written)
Image Paint Tool
(to be written)
Brush color
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Brush Diameter
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Brush Pressure
(to be written)
Brush Blending mode
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Stroke
Space
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Airbrush
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Curve
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Options
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Last command panel
This panel is on the bottom of the Toolbar and contains all the options of the last tool you use.
(to be written)