Control-drag $F\left(x\right)\=\dots$
Context Panel: Assign Function

Write $F\prime \left(x\right)$

Context Panel: Evaluate and Display Inline

Maple uses the D-operator to represent differentiation of functions. The object $\mathrm{D}\left(f\right)$ is the function $f\prime$, so it is evaluated at $g\left(h\left(x\right)\right)$, the "stuff inside;" similarly for $\mathrm{D}\left(g\right)$, the function $g\prime$, which is evaluated at $h\left(x\right)$, the "stuff inside $g$."

Thus, Maple knows how to implement the Chain rule, but it uses the compact D-operator notation.

The vertical stroke means "evaluated at" and its use in the first set of parentheses is the equivalent of writing, for example, $f\prime \left(g\left(h\left(x\right)\right)\right)$. Use of the prime for differentiation generally results in much more compact expressions.

Maple uses $\mathrm{t1}$ twice, the first time for $v\=g\left(h\left(x\right)\right)$; and the second, for $w\=h\left(x\right)$.

Again, Maple knows the differentiation rules, but the notation it uses to express them can sometimes require an explanation.