donot know how to provide circular co-ordinate but you can make a circle of desired radius in any mechanical layer and divide it by the line rotated at the angle in which you you want to place leds then you can place leds at the intersection of line and circle.
Suppose you want to place 8 leds in circle then draw a circle and place 8 lines at angle of 45 degrees and place lede at the intersection of led and circle.
Hopes it helps,
and if you get to know any other kindly let us also know.
Create your footprint, but position the component origin (pick point) the radius of your circle away, so when you select the component it will rotate around the circle centre.
If the LED's are to be positioned equally around the circle, then divide 360 degees by how many LED's you have and this becomes your rotation angle.
I have a doubt doing this.As it will also change rotation angle of componnent .
I think from manufacturing point of view leds should be in same orientation angle.