Only one legend can be assigned to an axes. This poses a problem if each axes has a legend and you want to add a global legend because there are no axes left to assign it to.
The solution is to create an invisible axes that is parented to the TiledChartLayout object. Then you can assign the global legend to that axes and specify the legend location using the tiled layout.
hiddenAxes = axes(tcl,'visible','off');
The second tip is the use the DisplayName property to assign legend strings to objects and then use the object handles to specify which objects go in which legend.
tcl = tiledlayout(1,2);
ax(1) = nexttile(tcl);
hold on
h = plot(sin(0:.3:12),'DisplayName','data1');
c = plot(abs(sin(0:.3:12)),'DisplayName','data2');
yl(1) = yline(0,'--','DisplayName','y=0');
% Apply legend to tile 1
legend(ax(1),yl(1))
ax(2) = nexttile(tcl);
hold on
plot(sin(0:.3:12),'DisplayName','data1');
plot(abs(sin(0:.3:12)),'DisplayName','data2');
yl(2) = yline(0.3,'--','DisplayName','y=0.3');
% Apply legend to tile 2
legend(ax(2),yl(2))
% Apply global legend
hiddenAxes = axes(tcl,'visible','off');
gleg = legend(hiddenAxes,[h,c]);
gleg.Layout.Tile = 'South';
gleg.Orientation = 'horizontal';
