How to create such points at the end of lines?

Question

Adobe Illustrator

How can you quickly, simply and elegantly create such points at the ends of lines, if you do not use a separate ellipse and append it? Maybe there is some tool or parameter for the line? Or create a brush?
There are so many functions and tools in the chandelier that maybe this has already been invented and there is no need to reinvent the wheel? The width of such a dot is 3-4px

Answer 1