In 2.6 I tried the new graphics layers but I was unable to make a text element shown as balloon callout. Doesn't matter what I set it does not show the leader line/arrow as a balloon callout should look like. Anybody has the same issue ?
In picture: "Subject" with yellow background is from label. "Subject" with gray background is from graphics layers. Same setting in balloon callout property. Thank you!
You should be able to see the leader if you select the graphic with the select tool on the map graphics tab:
and right click the text to select Add Leader:
You can then move around the anchor to your desired position. Hope that helps! Let me know if you have any issues.