Subnumber Individual Parts

Locate the autonumbered part you want to subunumber with an alphabetic suffix or a stencil associated with the part.

Note that for manually numbered parts, a subnumbering suffix may simply be typed into the part number field as part of the part number when the part is created.
Select the desired "Set number to" option from the menu available through the icon to the right of the part name in the Parts panel, the toolbar, the Element Info controls in the right-hand sidebar, or the on-canvas controls available when the stencil is double-clicked.
Parts will be subnumbered according to your selection.
Repeat for each part you want to include in a subnumbered set.

Note that if a part has been placed as a stencil on the drawing canvas, it can also be subnumbered using controls available to the right of the canvas when the stencil is selected.

Subnumber a Set of Parts

Locate the autonumbered parts you want to subnumber with an alphabetic suffix in the Parts Panel in the left-hand sidebar of the Drawing Tool.
Select all parts you wish to subnumber.
Click the Subnumber option from the multi-part operations menu at the top of the Parts Panel and select the presented subnumbering option.
Your selected set of parts will be subnumbered as indicated.

Locate the part you want to remove the alphabetic suffix from in the Parts Panel in the left-hand sidebar of the Drawing Tool.
Select the "Set number to" option from the menu available through the icon to the right of the part name in the Parts panel, the toolbar, the Element Info controls in the right-hand sidebar, or the on-canvas controls available when the stencil is double-clicked.

See above for additional menu location options.
The selected part will be moved out of the subnumbered set to the next available part number.

Note that if a part has been placed as a stencil on the drawing canvas, it can also be unsubnumbered using controls available to the right of the canvas when the stencil is selected.