The MarkerIndices property was introduced around R2016b. This allows you to specify which points have a marker. See this example
Here's what it might look like to add a red dot every 25 points.
x=0:100;
y = 2.5*x;
plot(x,y,'g.--','MarkerFaceColor','red','MarkerEdgeColor','red','MarkerIndices',1:25:length(y))
legend