To Create a Custom Button

Do one of the following:

Select File > Settings > User > Customize Ribbon .

or
Right-click in the blank space in the ribbon and select Customize Ribbon from the pop-up menu.

The Customize Ribbon dialog opens.
In the list below Customize the Ribbon, navigate to the desired workflow, tab, and the group in which you want to add the new button.
Click New Button.
(Optional) In the Properties section, set the following:
1. To change the label of the button, enter the new label in the Label field.
2. In the Key-in field, enter the key-in that should be executed when the button is selected.
3. To change the icon, in the Icon field, click the Browse button on the right-side. The Define Icon for Tool dialog opens, from where you can select the icon for the new button or menu-item.
4. To set the visibility, select the visibility expression from the Visibility drop-down list.
  Note: The Visibility property holds the name of a named expression that will be evaluated each time the active model is changed to determine whether the item should be displayed. The named expression should return a boolean (True or False) result in order to work properly as a Visibility property.
5. To set the enable/disable criteria, select the named expression from the Enable drop-down list.
6. Set other fields, as desired.
Click Apply.