Adjust the options via the shelf?
Can I open up the option box of a given command via clicking on it's icon in the shelf, ie I am going to merge vertices several times though I want to alter the tolerance, can I ctrl (example) + click the icon to bring up the option box to adjust the tolerance? Or do I have to fish around in the actual menu bar? I know I can bring up the option box by sometimes double clicking the icon but that already executes the operation with the wrong unchanged setting so you have to undo, then alter the settings.
If you believe in telekinesis, raise my right hand.