When using numbering in combination with the Flow Chart and the BPMN 2.0 view, there might be situations where the numbering mode does not look good. For that reason, you can change the numbering mode. The default numbering mode is the one better for the Flow Chart view, which is top to bottom and if there are any elements on the same level then left to right. But this mode would not be quite useful in the BPMN 2.0 view which is the reason why you can configure the mode to the BPMN 2.0 numbering mode. The numbering mode for BPMN 2.0 is from left to right and for elements on the same level, it is top to bottom. In addition to that, the numbering can also be done manually.
The numbering mode can be changed in the Settings which you can find in the Main tab under the section Model.
The opened wizard is separated into 3 sections, the one you can find the numbering mode settings in is the View section. Select the mode you would like to apply, and confirm with clicking the OK button.
With the manual numbering mode, you can also number just a few of the elements and not all of them. When configured the manual numbering mode, you have to select the element which number you would like to change and then enter the wanted number in the Property Panel under the General section.
If you leave the textbox empty or enter 0 then for this element, no number will be shown.