There are no power series objects in Maxima, just conversion to infinite sums, i.e. formal power series:

sage: maxima.powerseries(x^2+1/(1-x),x,0)
'sum(_SAGE_VAR_x^i2,i2,0,inf)+_SAGE_VAR_x^2
sage: maxima.powerseries(x^2+1/(1-x),x,0).sage()
x^2 + sum(x^i3, i3, 0, +Infinity)

The Taylor series objects have an order parameter on creation, but this does not get output or translated to Sage:

sage: maxima.taylor(1+x+x^2+x^3,x,0,3)
1+_SAGE_VAR_x+_SAGE_VAR_x^2+_SAGE_VAR_x^3
sage: maxima.taylor(1+x+x^2+x^3,x,0,3).sage()
x^3 + x^2 + x + 1

so there is no way around it that `SR`

.series will lose the order term when passed to Maxima. Thus only the coefficients may be simplified, and this must be done in or called from all `simplify*`

functions.