How to re-scale a matrix column and show the matrix in one line?

Why not use Dot instead?

p . DiagonalMatrix[{1, 1, 5}]

{{a, b, 5 c}, {d, e, 5 f}, {g, h, 5 i}}

q = MapAt[5 # &, p, {All, 3}]

{{a, b, 5 c}, {d, e, 5 f}, {g, h, 5 i}}

q = ReplacePart[p,  {i_, 3} :> 5 p[[i, 3]]]

{{a, b, 5 c}, {d, e, 5 f}, {g, h, 5 i}}

q = p.ScalingMatrix[{1, 1, 5}]

{{a, b, 5 c}, {d, e, 5 f}, {g, h, 5 i}}

p // ScalingTransform[{1, 1, 5}]

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