Affinity Photo Dash Line Patterns, just start from a basic diagonal path (hold down the shift to have it applied horizontal or vertically or diagonally. Personally, horizontally is the easiest start point.
You can add a stroke to a path, any path such as a straight line and set a stroke color of black etc and you can then go to the stroke drop down and the third option and go to the settings at the bottom and enter 1, 1, 2, 1 or 1.5, 1.4, 2.4, 2.6 and also set the phase as required.
Convert this design into a raster format via the layer menu and rasterize.
The rasterized design can then be used with the layer menu pattern layer from selection command and then that can be re-sized, transformed, rotated and much more. As the dash designs can be nearly infinite then the patterns can be.
Create a line using the pen tool etc and then go to the fill and set to nil via the swatches panel and then goto the strokes and then go to the third option (swatches, solid, dash line style) and then set the settings such as 1, 1, 2, 1, etc (this is at the bottom of the panel). You can also set the join, align etc to create a variety of different artworks.
You can also create multiple lines with different settings and then combine them via the merge visible in the layers menu and then use the pattern from selected command. You can set the color of the strokes to anything so you can generate red / black, green / blue / red etc artworks in seconds.