  We document major new features and improvements of FlexibleSUSY, a
Mathematica and C++ package with a dependency on the external package SARAH,
that generates fast and precise spectrum generators. The extensions presented
here significantly increase the generality and capabilities of the FlexibleSUSY
package, which already works with a wide class of models, while maintaining an
elegant structure and easy to use interfaces. The FlexibleBSM extension makes
it possible to also create spectrum generators for non-supersymmetric
extensions of the Standard Model. The FlexibleCPV extension adds the option of
complex parameters to the spectrum generators, allowing the study of many
interesting models with new sources of $CP$ violation. FlexibleMW computes the
decay of the muon for the generated model and thereby allows FlexibleSUSY to
predict the mass of the $W$ boson from the input parameters by using the more
precise electroweak input of $\{ G_F, M_Z, \alpha_{\text{em}} \}$ instead of
$\{ M_W, M_Z, \alpha_{\text{em}} \}$. The FlexibleAMU extension provides a
calculator of the anomalous magnetic moment of the muon in any model
FlexibleSUSY can generate a spectrum for. FlexibleSAS introduces a new solver
for the boundary value problem which makes use of semi-analytic expressions for
dimensionful parameters to find solutions in models where the classic two-scale
solver will not work such as the constrained E$_6$SSM. FlexibleEFTHiggs is a
hybrid calculation of the Higgs mass which combines the virtues of both
effective field theory calculations and fixed-order calculations. All of these
extensions are included in FlexibleSUSY 2.0, which is released simultaneously
with this manual.
