- Enable the Maplex Label Engine.
- On the Labeling toolbar, click Labeling > Key Numbering.
- Click New.
- Type a name for a new key number group.
- Click OK.
- Click the Horizontal Alignment drop-down arrow and specify how the group should be aligned.
The default is Automatically choose best. The other options are Constrain to left and Constrain to right.
- Click the Number Reset drop-down arrow and specify if the key number is to be reset for each group.
The default is No Reset; with this option the numbers for the key items will be incremented through the map. The other options are May Reset, where the number is reset depending on the size of the group and the distance from other groups, and Always Reset, where each key group starts with 1.
- Enter a Delimiter Character which will separate the key number from the label.
- Specify the Minimum number of lines and the Maximum number of lines for your key groups.
- Click OK.
You can now edit the properties of the group.