Move existing subscription items between subscription groups

I have two existing subscription groups in iTunes connect which is in released state from last 3 years. Now, i want to combine all the subscription items into a single subscription group without impacting the users who has already subscribed.

But, i don't see an option to move these subscription items between groups.

My question here is how could we efficiently combine these subscription items from diffrent group into a single group?

Any help would be appreciated.

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