Can not toggle btnm button from different button

I have been working on btnm buttons and I have a problem with to toggle from outside of btnm button.
I mean toggle btnm button to not touch btnm buttons.
To be clear:
I have a screen and one btnm button in the center and mapping 3 elements like {“A”,“B”,“C”,""}
and I have two different buttons on the left and right side of screen.
So I want to toggle any of btnm buttons using left or right buttons.
I have tried couple scenarios but did not worked for me.
Can you help.

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