You can sub-number any parts from the same figure or figure group (e.g. FIG 1A, 1B).
Create Sub-numbered Part Group in a Figure
Select the part or parts on the canvas you want to sub-number.
In the Element description panel, select the "Sub-number part with..." checkbox.
From the drop-down menu, select the part you want to be sub-numbered with "a".
For example, if you want to convert parts 802, 804, and 806 into a sub-numbered group of 802a, 802b, 802c, select the three parts on the canvas, click the "Sub-number part with..." checkbox and select part 802 from the drop-down menu.
NOTE: Parts will be sub-numbered in the order you select them on the canvas.
e.g. If you click part 802, 806, 804 in that order, 806 will convert to 802b, and 804 will be 802c.
Add More Parts
You can add more parts to the group by selecting the part, and then selecting the sub-numbered part you want that part to follow. For example, if you add part 808 in FIG 8B to the group of 802 sub-numbered parts, select part 808 on the canvas, click the Sub-number checkbox and select part 802c to change 808 to 802d.
If you wanted to convert part 808 to 802b, you would select 802a instead. That would increment the sub-numbering on the subsequent parts.
Remove Part Sub-numbering
Select the sub-numbered part or parts and deselect the "Sub-number parts with... " checkbox.
Re-ordering Sub-numbered parts
In the numbering panel, sub-numbered parts are displayed as a group. You can reorder the part group. For example, if you wanted to re-order sub-numbered parts 802a, 802b, 802c with part 804, select the part group and drag it below 804.
To reorder within the group, select the part you want to re-order and deselect the Sub-number part checkbox then re-check it and select the sub-numbered part you want it to follow.