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Using the Mouse in the Equation Editor
Left Mouse Button
You can use the LEFT mouse button for a variety of functions. For example:
Click the LEFT mouse button on a symbol or construct to outline it with a marker that points to where the next construct will be inserted.
Click the LEFT mouse button on any symbol or construct to get rid of any existing highlighting and cancel replace mode.
In the Palette, click the LEFT mouse button on the appropriate Palette button to insert the symbol or construct into the location indicated by the outline
In the Palette, click the LEFT mouse button on the appropriate Palette button to apply the operation signified by the button.