Can I Type This With My Left Hand?
Python 3, 48 bytes

Takes as input \$ K \$ and \$ S \$, the keyboard and the target string. \$ K \$ is a taken as a list of lists.



lambda K,S:{r.pop(0)for r in K for i in r}&gt;={*S}


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Explanation

It essentially converts \$ S \$ and the valid keyboard characters \$ K' \$ into sets, and returns True iff \$ S \$ is a subset of \$ K' \$. To obtain only the first half of each row of \$ K \$, we use the pop trick, which is explained in this answer of mine.



The previous answer, where \$ K \$ is taken as a list of strings instead.

Python 3, 54 bytes



lambda K,S:{*''.join(r[:-~len(r)//2]for r in K)}&gt;={*S}


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