Step 1: Use the direct ratio shortcut for axis intersection.
When a segment joining $(x_1,y_1)$ and $(x_2,y_2)$ is cut by the $y$-axis, the ratio of division (from the first point) is $-x_1 : x_2$.
Step 2: Plug in the given coordinates.
Here $P(-4,-2)$ and $Q(10,4)$, so
\[ \text{Ratio} = -(-4) : 10 = 4 : 10 \]
Step 3: Simplify the ratio.
\[ 4 : 10 = 2 : 5 \]
Step 4: Conclude.
The $y$-axis divides $PQ$ in the ratio $2:5$, matching option (1).
\[ \boxed{2:5} \]