 Here is a basic example of how you might set up a combined fluid-kinetic simulation using the DREAM library, as per your instructions. Please note that this is a simplified example and may need to be adjusted to fit your specific needs.

```python
from dream import *

# Set simulation parameters
electric_field_strength = 1e5
electron_density = 1e19
temperature = 1e6

# Generate momentum grid
momentum_grid = _generateMomentumGrid(num_points=100, min_momentum=0, max_momentum=1e6)

# Define initial hot electron Maxwellian
hot_electron_distribution = HotElectronDistribution(temperature=temperature, density=1e12)

# Set up Dreicer and avalanche in the equation system
include(Dreicer())
include(Avalanche())

# Set up radial grid and disable runaway grid
radial_grid = RadialGrid(num_points=100, min_radius=0, max_radius=1)
setCustomGrid(radial_grid)
setGrid(Grid.RUNAWAY_ELECTRON, enabled=False)

# Set up hot-tail and Svensson transport coefficients
setCustomGridPoints(Grid.HOT_TAIL, [0.1, 1, 10])
setHottail(electron_density=electron_density, temperature=temperature)
setSvenssonTransportCoefficients()

# Use nonlinear solver
setSolver(NonlinearSolver())

# Set up time stepper
setTimeStepper(TimeStepper.BACKWARD_EULER)

# Save settings to an HDF5 file
with HDF5File('simulation.hdf5', 'w') as file:
    file.write(getTimeAndUnit(), '/simulation/time_and_unit')
    file.write(formatTimeAndUnit(electric_field_strength, 'V/m'), '/simulation/electric_field_strength')
    file.write(formatTimeAndUnit(electron_density, '1/m^3'), '/simulation/electron_density')
    file.write(formatTimeAndUnit(temperature, 'eV'), '/simulation/temperature')
    file.write(momentum_grid, '/simulation/momentum_grid')
    file.write(hot_electron_distribution, '/simulation/hot_electron_distribution')
```

This code sets up a simulation with the specified parameters, including the electric field strength, electron density, and temperature. It also includes Dreicer and avalanche in the equation system, sets up the radial grid and disables the runaway grid, sets the Svensson transport coefficients, uses the nonlinear solver, and sets up a time stepper. The settings are then saved to an HDF5 file.