Photoshop : How To Customize Tools Tutorial | Graphicxtras
Go to the edit menu and toolbar OR go to the panel and click the little ... and use the edit command from there. You will then see the dialog with all the available features such as move, art board, marquee, lasso, frame etc
The panel displays all the active items on the left, all the extra ones (not active) on the right.
Move items from active to not active
You can drag the items from one side to the other and vica versa, so you can use it to remove them from the main active set. Select and drag from the active and drop when you are over the inactive. You can go to the inactive and then select / drag and then release in the active
You can select an item and drag the item from one group and place it in another. As you hover over a group and you see a little blue line appear, release and that will be then added to that. You can also select an item currently in a group and drag it out and place in another or just hover a blank area and it will be just given its own slot and not connected with any other item. You can place it next to the existing items or drag it down to the bottom and the item will be added to the panel at the bottom. You may decide that the ruler / count / measurement etc work well together so you can drag each of them on top of the existing and they will then also be grouped.
You can also re-order all the items with sections or just over the entire panel. Say that you use the custom shapes more than anything else well you can go to the rectangle / ellipse section and drag the custom shape from that and place right at the top or close to the top of the list in a group of its own and you will see it then a single item close to the top of the panel and easily accessible. Perhaps you don't use the note item as much but still want it to be available in the active set (I prefer to keep everything active) but I don't use the note that much and it can be dragged to the bottom of the panel. Or the ellipse can be placed above the rectangle and the triangle placed at the bottom of the section etc. Simply select and drag and place.
You can also go to the bottom and click on the show items to make them active or not such as the extras, foreground / background as well as screen mode and quick mask. You can also disable the shortcuts of the hidden one (the ones in the right column) as there are limits to the number of shortcuts.
You can restore the defaults via the right side buttons in the panel. If you are unhappy with your setup, just click that to put it back to normal. Clear is quite dramatic but it does mean that everything goes into the hidden and you can start afresh and drag out the tools that you really use, be useful for say a tutorial where you only want to show a small set of options such as note, measurement, etc. You can also save the current set to a TBR format file and store it in a preset location. You can then click the load and load it later so if you have certain things available for certain tasks, you can bring them back in again in seconds. Cancel, just leave. Done, that is it, you are committed for now with the latest set.