Hello,
When you say that you have a value for each element, do you have an analytic _expression_ for that, or do you have something like a list with element number --> value?
If you have an analytic _expression_ then you can use md.interpolation(....) to assign your source data to a model variable. Something like this (assuming that your problem variable is called u):
N = m.dim()
mf = gf.MeshFem(m,N)
mf.set_classical_fem(0) # zero degree fem, i.e. discontinuous
...
md.add_fem_data("source", md.interpolation(".....", mf, RG_ID))
md.add_linear_term(mim, "source.Test_u", RG_ID)
BR
Kostas