This one is very tricky. You can’t just set the value to * (no quotes) by typing it into a ValueSpecificationAction symbol; you have to use the specification dialog, and then under Value use the small right arrow to go to Value Specification > Literal Unlimited Natural (which fills in a 0 by default) then change it to * (no quotes).
For correctness one should then also set the 'result' OutputPin on the ValueSpecification and the 'insertAt' InputPin to have type UnlimitedNatural and multiplicity 1..1, but Magic Model Analyst® (Cameo Simulation Toolkit®) does not seem to care about that.)