Certainly! Let's break down the requirements for the test case generator for the given problem. Here's the plan:

1. **Number of vertices \(N\) and edges \(M\)**: The problem mentions that \(N \leq 300\), and there should be no self-loops or multiple edges.
2. **Edge weights/labels**: Each edge can have a weight between 0 and 100 or a label 'X' or 'Y'.
3. **Shortest paths \(d_{x,y}\)**: These are given for any pairs of values \(x\) and \(y\) such that \(1 \leq x \leq A\) and \(1 \leq y \leq B\). The values of \(d_{x,y}\) are between 1 and 100.

The generator will randomly create valid input values for \(A\), \(B\), and the matrix \(d\). Here’s the code for the test case generator:

```python
import random

def tcgen():
    # Randomly choose A and B within the constraints
    A = random.randint(1, 10)
    B = random.randint(1, 10)
    
    # Generate the d matrix with values between 1 and 100
    d = [[random.randint(1, 100) for _ in range(B)] for _ in range(A)]
    
    # Convert the matrix to the required input format
    d_flat = '\n'.join(' '.join(map(str, row)) for row in d)
    
    # Assemble the input
    input_str = f"{A} {B}\n{d_flat}"
    
    return input_str

# Example usage:
print(tcgen())
```

### Explanation
- **Randomly choose \(A\) and \(B\)**: Both \(A\) and \(B\) are chosen randomly between 1 and 10.
- **Generate the \(d\) matrix**: The matrix \(d\) of size \(A \times B\) is filled with random integers between 1 and 100.
- **Format the matrix for input**: The matrix is converted to a string format suitable for the input, where each row is space-separated and rows are newline-separated.
- **Return the input string**: The formatted string is returned.

This generator will create various test cases for the problem, ensuring diverse and comprehensive coverage of the possible input space.