Thank you Sergio. The new method gives the same error

SystemModel::irl: The list of rules is not on the form {"variable" -> numericValue, ...}.

I'll email you about the bugs.

B

Thank you Sergio but I cannot get your solution to work. Please see the Minimal Working Example (MWE)

comp = {"world" \[Element] "Modelica.Mechanics.MultiBody.World", 
   "transf" \[Element] "Modelica.Mechanics.MultiBody.Parts.FixedRotation", 
   "box" \[Element] "Modelica.Mechanics.MultiBody.Parts.BodyShape"};
conn = {"world.frame_b" \[DirectedEdge] "transf.frame_a", 
   "transf.frame_b" \[DirectedEdge] "box.frame_a"};

mdlName = "TestIt";
ConnectSystemModelComponents[mdlName, comp, conn]

SetSystemModel[
  mdlName, <|
   "ParameterValues" -> {"transf.rotationType" -> 
      QuantityVariable[
       "Modelica.Mechanics.MultiBody.Types.RotationTypes.
PlanarRotationSequence", IndependentPhysicalQuantity[""]]}|>];

This MWE gives the following error:

SystemModel::irl: The list of rules is not on the form {"variable" -> numericValue, ...}.

If my syntax is correct then there might be some unexpected behavior from SetSystemModel for enumeration types. I wonder if it's a bug that I should report.

To make progress on my project I have worked around the problem like so: after all model parameters are set: 1) assign the "Modelica.Mechanics.MultiBody.Types.RotationTypes. PlanarRotationSequence" string to all rotationType parameters, 2) extract the ModelicaString of the model; 3) find the string position of all rotationType; 4) remove the enclosing double quotes " and 5) save the ModelicaString to a text file of extension type .mo. It ain't pretty but it gets the job done.

If it's of any help I am using Matematica 12.1.0.0 and SystemModeler 12.2.0, build 8. I cannot update to Mathematica 12.2 because it has other bugs that crash other notebooks.

B