You can control the branching priorities in Gurobi using the BranchPriority attribute, which you can then store in an .ord file.
This file can then be provided as an input using the InputFile parameter.
If you cannot add a parameter through the pyomo API, you can always create a gurobi.env file in the directory where your script is located and store all your parameter modifications there.
InputFile parameter cannot be added as a parameter in the
gurobi.env. Instead, you should follow @Oguz's approach:
msolver.options['InputFile'] = '<path-to-ord-file>'