Feature request - User defined variables, constraints and costs

MOST does not support adding custom user-defined constraints, yet.
Indeed MATPOWER allows that through the "add_userfcn" function, but MOST doesn't

The work-arounds I could think of are:
add new constraints and costs manually
Building the MOST model, without solving it. that is: set the mpoptions to:
most.build_model = true; most.solve_model = false;

Use the functions:
build the A, L, U and VS variables to add a new constraint; using the functions: init_indexed_name and add_lin_constraint. To understand how they work, you need to take a deep look at the MOST.m file

Set:
build_model = false;
solve_model = true;

and call MOST a second time, with your modified model as the input to MOST
There is currently a bug that would prevent this. I reported this bug in a separate earlier issue. The bug-fix is also mentioned there.

Note:
you have to add you new constraints and variables with the commands:
init_indexed_name and add_lin_constraint.
modifying the matrices: mdi.QP.A, mdi.QP.l, mdi.QP.u
would not work, because these matrices are over-written inside MOST.m

The developers of MOST.m may want to change that behavior, because generating mdi.QP takes a lot of time for large models.

a messy workaround is to build your own A, l and u and call the solver manually and outside most.m, that is:

if UC
[mdo.QP.x, mdo.QP.f, mdo.QP.exitflag, mdo.QP.output, mdo.QP.lambda ] = ...
miqps_matpower( mdi.QP.H, mdi.QP.C, mdi.QP.A, ...
mdi.QP.l, mdi.QP.u, mdi.QP.xmin, mdi.QP.xmax, ...
[], mdi.QP.vtype, mdo.QP.opt);
else
[mdo.QP.x, mdo.QP.f, mdo.QP.exitflag, mdo.QP.output, mdo.QP.lambda ] = ...
qps_matpower( mdi.QP.H, mdi.QP.C, mdi.QP.A, ...
mdi.QP.l, mdi.QP.u, mdi.QP.xmin, mdi.QP.xmax, ...
[], mdo.QP.opt);
end

I am currently working on a few papers and have already implemented several cases of custom constraints, new variables and new costs.
Once the paper is published, I'll share these along with a brief explanation.
An example of a constraint which isn't currently supported is:

• Minimum-up-time and minimum-down-time are already implemented

but there is no constraint for: maximum-up-time!

• Prevent two machines from being committed together at the same time
  i.e. u_1 + u_2 <= 1

Start by reading MOST.m and the existing init_indexed_name and add_lin_constraint paths. Trace how the model is built and how mdi.QP.A, mdi.QP.l, and mdi.QP.u are regenerated, then review the separate earlier bug report referenced in the issue. Done would mean a decided design and documented support for user-defined variables, constraints, and costs without relying on manual solver calls.