In quadrilateral $ABCD$, we have $AB = 5$, $BC = 6$, $CD = 5$, $DA = 4$, and $\angle ABC = 90^\circ$. Let $AC$ and $BD$ meet at $E$. Compute $\dfrac{BE}{ED}$.
1. **Identify the coordinates of points in the quadrilateral:**
   - Since $\angle ABC = 90^\circ$, we can place $A$ at $(0, 0)$, $B$ at $(5, 0)$, and $C$ at $(5, 6)$ in a coordinate system.

2. **Determine the coordinates of point $D$:**
   - We know $DA = 4$ and $CD = 5$. Let $D$ be at $(x, y)$. We have two equations from the distances:
     \[
     \sqrt{x^2 + y^2} = 4 \quad \text{(1)}
     \]
     \[
     \sqrt{(x-5)^2 + (y-6)^2} = 5 \quad \text{(2)}
     \]

3. **Solve the system of equations:**
   - Square both equations to eliminate the square roots:
     \[
     x^2 + y^2 = 16 \quad \text{(3)}
     \]
     \[
     (x-5)^2 + (y-6)^2 = 25 \quad \text{(4)}
     \]
   - Expand equation (4):
     \[
     x^2 - 10x + 25 + y^2 - 12y + 36 = 25
     \]
     \[
     x^2 + y^2 - 10x - 12y + 61 = 25
     \]
     \[
     x^2 + y^2 - 10x - 12y = -36
     \]
   - Substitute $x^2 + y^2 = 16$ from equation (3):
     \[
     16 - 10x - 12y = -36
     \]
     \[
     -10x - 12y = -52
     \]
     \[
     5x + 6y = 26 \quad \text{(5)}
     \]

4. **Solve for $x$ and $y$:**
   - From equation (5):
     \[
     5x + 6y = 26
     \]
   - Express $x$ in terms of $y$:
     \[
     x = \frac{26 - 6y}{5}
     \]
   - Substitute $x$ back into equation (3):
     \[
     \left(\frac{26 - 6y}{5}\right)^2 + y^2 = 16
     \]
     \[
     \frac{(26 - 6y)^2}{25} + y^2 = 16
     \]
     \[
     \frac{676 - 312y + 36y^2}{25} + y^2 = 16
     \]
     \[
     \frac{676 - 312y + 36y^2 + 25y^2}{25} = 16
     \]
     \[
     676 - 312y + 61y^2 = 400
     \]
     \[
     61y^2 - 312y + 276 = 0
     \]
   - Solve the quadratic equation for $y$:
     \[
     y = \frac{312 \pm \sqrt{312^2 - 4 \cdot 61 \cdot 276}}{2 \cdot 61}
     \]
     \[
     y = \frac{312 \pm \sqrt{97344 - 67224}}{122}
     \]
     \[
     y = \frac{312 \pm \sqrt{30120}}{122}
     \]
     \[
     y = \frac{312 \pm 173.6}{122}
     \]
     \[
     y = 4 \quad \text{or} \quad y = 1.13
     \]
   - For $y = 4$:
     \[
     x = \frac{26 - 6 \cdot 4}{5} = \frac{2}{5} = 0.4
     \]
   - For $y = 1.13$:
     \[
     x = \frac{26 - 6 \cdot 1.13}{5} = \frac{19.22}{5} = 3.84
     \]

5. **Determine the correct coordinates of $D$:**
   - Check which coordinates satisfy both distance conditions:
     - For $(0.4, 4)$:
       \[
       \sqrt{(0.4-5)^2 + (4-6)^2} = \sqrt{21.16 + 4} = \sqrt{25.16} \neq 5
       \]
     - For $(3.84, 1.13)$:
       \[
       \sqrt{(3.84-5)^2 + (1.13-6)^2} = \sqrt{1.34 + 23.74} = \sqrt{25.08} \approx 5
       \]
   - Thus, $D$ is approximately at $(3.84, 1.13)$.

6. **Calculate the ratio $\frac{BE}{ED}$:**
   - Use the ratio lemma:
     \[
     \frac{BE}{ED} = \frac{AB \cdot \sin(\angle BAD)}{AD \cdot \sin(\angle DAB)}
     \]
   - Since $\angle BAD = 120^\circ$ and $\angle DAB = 60^\circ$:
     \[
     \frac{BE}{ED} = \frac{5 \cdot \sin(120^\circ)}{4 \cdot \sin(60^\circ)} = \frac{5 \cdot \frac{\sqrt{3}}{2}}{4 \cdot \frac{\sqrt{3}}{2}} = \frac{5}{4}
     \]

The final answer is $\boxed{\frac{5}{4}}$