Add more Markers on Labeled Graphic

Thank you for this question and video.  I was struggling to add additional markers as well.  

Also weighing in, here, that this workflow is not even remotely intuitive, especially since to add more buttons in a button block, or to add more items in a list, the sidebar menu provides an "Add item" option (which serves as an instruction). I, like others for years here, (apparently) was looking for this conventional 'add' feature. You could simply add an instruction in the sidebar in the 'Edit' window below the intial 2 markers provided (i.e., in the same location as the "Add item" instruction in other places) to the effect of, "Click on image to add more labels". Since people will see that instruction when the 'plus sign' icon is active, it should be more readily evident that that's what one is supposed to do. As it is, there are no instructions at all for adding a new label.

how do you add double numbers on the markers?

How to add 10 and more in marker style?

Several have enquired about adding numbered markers beyond "9" but I haven't seen a good response to this.  I need to use numbers as it's easier when referring to specific call-outs but find myself stuck in certain use cases where I must exceed 9!  In fact, for one project, I need at least 12.   Seems like an easy update to accommodate!