hi softy (or is it Mr. 123__?)
strokes are dynamic streams, and are handled by the dynamicStreamSuite.
with that suite you can add remove and alter strokes and text layer params.
but if you want to create some new custom params that behave like the storkes, then it can't be done through the API.
i can give you 2 solutions.
lets say you want each new "stroke" to have 4 params: width, length, start and end.
then you could:
1. create your effect with 50 hidden groups, each with these 4 sliders in them.
and then unhide each group as necessary.
the user will just see new params pop up, without knowing they were there all along, hidden.
this is the easiest method.
it's only restricted by the amount of hidden groups you compiled your plug-in with.
2. create a dummy effect with these 4 sliders, and add new instances of that dummy to the layer, whenever you need more "strokes".
this method is more flexible than the first, as no redundant params exist, and you can add as many as you want.
however it's much much more complex to pull off.
that's the best a could come up with.
i hope this helps.
:-)