To Create a New Split Button from an Existing Split 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 group in which you want to create the split button.
In the Choose components from drop-down list, select Split Buttons.
Do one of the following:

From the list below Choose components from, select the desired split button and then click Add.

or
From the list below Choose components from, select and drag the desired split button to the list below Customize the Ribbon.
(Optional) Do one of the following:

Click Rename and rename the new split button.

or
Rename the new split button in the Label field in the Properties section.
(Optional) In the Properties section, from the Visibility drop-down list, select the visibility expression.
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.
(Optional) Set other properties, as desired.
Click Apply.