How to restore Illustrator missing tools or get back your favorites, say a particular one is missing from your panel ?? How to restore it or reset them ?
The tools bar can be edited by going to the bottom of the panel and clicking the '...' This will display a list of all available, all grouped in different categories.
Scroll down this list and find your favourite there and if it is highlighted then you can drag it back into the tools bar and position it where you want either in a group or on its own and at the top or in the middle or at the bottom thus restoring your favourite missing one or two
While you are in edit mode, you can also drag the existing ones in the tools bar around so if you use a particular tool more than another then you can move those to a better position. While in edit mode, you can also move your least favourite (graphs for me) into the list and take them away from the main bar
In the edit panel, you can also go to the top right of the panel and select the menu and reset all everything back to the factory default as well as move between the basic set where Adobe decides which are key or the advanced which gives you the full set. In either mode, you can still remove and move and add.
The same panel also offers the option to create your own tools bars and manage them as well.. You can then set up one that has the rectangle, ellipse, shape builder etc in one place and makes it super easy to access your favorites