Question: How to replace a specific list/set entry?

I am trying to replace thickness = 0 with thickness = 3 in a list, under the condition leader = 0 

The order of entries in the list is not fixed so it is more akin to a set.


parms:=[colour=red,thickness=0,linestyle =dash];
 if leader=0 then selectremove(thickness=0,parms);end if;
display(plottools:-line([1,2], [3,4]),op(parms));
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