Pokemon Let's Go - What is the greyed out button in play with partner menu?
Solution 1:
As shown circled below, the second option in the partner play menu is for Secret Techniques. Secret Techniques are the HM equivalents from the main series games, allowing you cut down trees, move boulders, etc..
It will be grayed out until you learn your first secret technique. If I remember correctly, this is during the events on the S.S. Anne, and speaking to the captain.
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