I created a brush following the advice of How to make the brush with the side of an even size (GIMP)? and from that tutorial https://www.gimp.org/tutorials/Custom_Brushes/.
I got what I wanted (in part).
When I make lines (click + shift + click) an error occurs.
Apparently the center of the brush is not set correctly, and the worst is that it varies depending on the entire image. Short lines do not change, the problem is evident when I make longer lines.