Meta-Parameter Mapping / Parameter Map / Edit Mapping...
Parameter [name length pushes pulldown choice button outside the window]
Some vsts have apparently reserved string lengths for their parameters that are too long for the little [Edit Mapping] window. As a result you cannot use the pulldown and would have to click through 100s of parameter names, hoping you find the one you're looking for.
Use some "max length" limitation for that window's [Parameter] string!