Cannot add equals to relationship in smart dimetion

Hello,

I'm experiencing a glitch where I cannot add equals to relationship in smart dimension. Please see that attached picture. in the picture I am editing the dimension on the left and adding an ="D1@Sketch1" command. D1 is the dimension on the top. When I press the green check mark to fish the edit nothing happens i have tried rebooting solid works but nothing seems to work. Has anyone else come across this issue?

Thanks for the help.

Cheers,

SolidworksParts And Features