Litz wire modelling allows you to specify the wire type, number of strands, and various other parameters that define the shape of the Litz wire bundle. There are three options Round, Square, and Rectangular, possible shapes for a Litz wire. For Eg, if you are modelling round, for entering twisting structure length you can enter detail in twisting length factor. Where twisting Length factor is the ratio of the twisted-strand length to the bundle length. To know more about Litz wire modeling refer the help documentation : Maxwell Help > Assigning Materials > Adding New Materials > Litz Wire Modeling and Please refer to the below blog on Litz wire in Maxwell 2D and 3D : Using Litz Wire in Maxwell 2D and 3D Simulations (ansys.com)
I hope this helps.