Question: Working with expressions from the Layout palette

Is there a way to to do the following:

such that Uranium containing the presubsup expression  displays the values contained in A, Z and X instead of just the letters?

(Edit):

I can, however, get it to work using the (A)[b]^(c) expression  from the same palette:

Though I don't understand why it works with one and not the other.

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