The points $P,$ $Q,$ and $R$ are represented by the complex numbers $z,$ $(1 + i) z,$ and $2 \overline{z},$ respectively, where $|z| = 1.$  When $P,$ $Q$, and $R$ are not collinear, let $S$ be the fourth vertex of the parallelogram $PQSR.$  What is the maximum distance between $S$ and the origin of the complex plane?
Let $w$ be the complex number corresponding to the point $S.$  Since $PQSR$ is a parallelogram,
\[w = (1 + i) z + 2 \overline{z} - z,\]so $w = 2 \overline{z} + iz.$  Then $\overline{w} = 2z - i \overline{z},$ so
\begin{align*}
|w|^2 &= w \overline{w} \\
&= (2 \overline{z} + iz)(2z - i \overline{z}) \\
&= 4 z \overline{z} + 2iz^2 - 2i \overline{z}^2 + z \overline{z} \\
&= 5|z|^2 + 2i (z^2 - \overline{z}^2) \\
&= 2i (z^2 - \overline{z}^2) + 5.
\end{align*}Let $z = x + yi,$ where $x$ and $y$ are real numbers.  Since $|z| = 1,$ $x^2 + y^2 = 1.$  Also,
\begin{align*}
2i (z^2 - \overline{z}^2) &= 2i ((x + yi)^2 - (x - yi)^2) \\
&= 2i (4ixy) \\
&= -8xy,
\end{align*}so $|w|^2 = 5 - 8xy.$

By the Trivial Inequality, $(x + y)^2 \ge 0.$  Then $x^2 + 2xy + y^2 \ge 0,$ so $2xy + 1 \ge 0.$  Hence, $-8xy \le 4,$ so
\[|w|^2 = 5 - 8xy \le 9,\]which implies $|w| \le 3.$

Equality occurs when $z = -\frac{1}{\sqrt{2}} + \frac{i}{\sqrt{2}},$ so the maximum distance between $S$ and the origin is $\boxed{3}.$