In the drawing resources folder of your model tree, RMB on the sketched symbols folder. Select "define new symbol" from the pull down menu. Draw a circle, select "property field" from your drawing sketch panel. Select "prompted entry" from the "type" box. Type in a prompt (i.e. X, #, Number, Letter, etc...). Hit OK. Place the text box in the center of the circle. Click return. Give the new symbol a name and click save. You can now place the symbol from the drawing annotation panel using the symbols tool. There is a toggle for leader or no leader.
David