For your purposes here, I would think that the easiest is to use the DisplayName property on the objects. That matches the string that the legend is showing.
Consider this example:
%%Create a plot with a legend
plot(magic(5))
legend('first','second','third','fourth','fifth')
%%Get a handle to the legend
%
% The type has changed because legends are no longer axes.
%
l = findobj(gcf,'Type','legend')
%%Loop over the legend entries and set the linewidth of the corresponding object
%
% Our legend has five strings. Each line object has a DisplayName which
% matches one of those strings.
%
for ix=1:length(l.String)
str = l.String{ix}
h = findobj(gcf,'DisplayName',str);
h.LineWidth = ix;
end
The result looks like this:
It looks like you might already know the DisplayName of the object you're looking for. If that's the case, you could skip getting the legend completely.
