We can make complex line meshes and even smooth them passing the coordinates into the Make Spline node. But it’s very hard to ‘fill’ the region outlined with either colour or image.
The closest I can get is to make a series of many quads by processing the coordinate list but it’s pretty laborious stuff and I haven’t attempted to make a universal subcomp to take any list of points. In any case this approach wouldn’t support image or gradient fills, it would only be possible with the same colour and fill for each quad. The edges between quads may been showing as edges where you’d want them to be seamless. Will investigate further…
Nice to have would be an auto-close-path option for open paths, stroke outline, smooth corners on outline with chamfer or radius, dashed line pattern (with user input for length of strokes and gaps not the random generator approach of kineme GL Line Tool). But just filling a polygon with color, gradient shader or an image would be freaking awesome.