Rather than make various different buttons on my toolbar, it would be
much easier for users to press one button and toggle navigating to 2
specific and going back to A2 at last toggle. Can this be done?

i.e., from startpoint (whatever it is) go to D2
from D2 to G2 and then each time pressing navigation goes backwards:
G2 to D2
D2 to A2

Thanks! :oD