Go to the tools panel and select the Affinity Designer pie tool. As with many of these, you can create the shape (it is a vector, there is no pixel mode but you can always use the layer menu and rasterize to turn it into a pixel layer)
You can manipulate it via the control bar such as change the fill and stroke (such as a solid color, gradient etc) as well as add dash settings to it as well as pressure settings to create interesting 'drawn' look to the art as well as adding brush strokes to it via the last tab in the stroke (and brushes panel)
Change the hole radius and start angle and end angle and total angle and there is also a very useful invert angle and close pie button. Change the start angle and end angle and the total angle will also change, they are linked. You can also modify all these settings via the little red dots on the vector itself and you can use it to create all kinds of wonderful designs such as thin designs, small arcs and more.
You can also stretch and squeeze the artwork and also rotate the artwork as well as shear it and you can still use it to interactively change the art. You can still set all the values for the hole radius as well as start angle and end angle (total) as well as invert and close
Once you have created your design you can also continue to work with it live or you can expand it to the nodes via the convert to curve button.
you can then tweak the node points by using the node. You can also duplicate the shape, create multiple instances by holding down the alt / option key.
You can add layer effects to the artwork by going to the layers menu and clicking the fx button at the bottom.
You can click the close button in the control bar and you can turn the design into a ring. You can still change the start and end sliders but the hole radius is more effective and you can set the radius to close to the size of the artwork or create a design with a small hole in the center by setting the value to 5% etc. You can interactively modify the radius as well
You can use the contour to add all kinds of edges to the design. Select the design and use the interactive option or the control bar to set the radius and angles and then go to the contour and apply a forced open to create a split in the art, you can also then click the bake appearance button in the control bar to freeze the design and this will convert the artwork to a normal curve and you can then manipulate it via the node and add additional points and tweak those around the edge of the shape. You can also go to the layers panel and click the fx at the bottom and add a 3D / bevel as well as a shadow etc. Go to the appearance panel and click the add new stroke and add multiple strokes which can be filled with different colors as well as have additional brush strokes added. The artwork can also be save for future use or if you wish, click the edit in photo command in the file menu and then add effects such blurs etc to the design. You can also use the node to manipulate the points on the curve as well as select actions such as break curve to split the path into two open paths.