How to use the turn a vector shape into a hand drawn / sketched design in Affinity Photo by using the powerful break curve action in Affinity.
The vector design can be created in many ways such as using the powerful vector tools such as diamond, ellipse, cog etc as well as using the pen tool. Set the fill to nil, set the stroke to black etc and also set a stroke width as well as a style such as changing the pressure for the design
The design needs to be displayed as nodes and not as an interactive shape. Go to the convert to curves command by right clicking or clicking the button in the control bar while selecting the shape. If it has been created using the pen tool etc then the nodes will already be available.
Use the node tool and select all the nodes of the current curve. Go to the control bar and the action section and click the break curve button.
Select the curves and then go to the stroke width and style and change and in particular go to the pressure panel inside the stroke settings and alter the contour of the pressure by moving the points up and down to narrow or increase the size of the stroke and this will be applied to all the curves.
If you don't want it to be the same across the entire design, select different parts of the design by clicking one or more of the curves in the layers panel and then manipulating the pressure as well as the stroke color etc for those paths.
You can if you wish then select all the curves and group them by right clicking and select group command. You can then also also add in the original vector path if you wish and place it behind or above (perhaps change transparency etc) and combine the hand sketched with the clean lines of the original vector design such as a cog and the hand drawn sketched cog art in Affinity Photo.