Brushes and pencils on the canvas
Sketch a path or paint pixels, in the same file as your layout.
Some ideas start as a scribble. Now the scribble can live next to the finished layout.
Pencil
Press N and draw. The Pencil makes real vector paths you can clean up with the Node tool.
Brush
Press B to paint on raster layers. Pair it with the Retouch tool on J to clean up photos.
Same file
Sketches, paint, photos, and vectors all sit on one canvas. No round trips between apps.