Erase Blend With Shapes Paths In Affinity Photo | How To | Transparent Background | Graphicxtras
Go to the tools panel and add some points to an image using the pen tool. Create a closed path. Go to the layers panel and select the created curve and set the fill color for the path to blue / green etc and then go to the blending modes and set the erase (should be at the bottom) and you will see transparency, you will have punched through the layer.
Multiple image layers
If you have multiple layers and create a curve and apply the blending mode, you will not see through to the others, you will always only see the transparency.
Add multiple curves
Click the Add new curve to selected curve object and now go back to the pen tool and add more points but in a different position of the image and they also will have the same effect. Always remember once you have finished the path to press escape otherwise you may get a line appearing across the screen. You can repeat that multiple times to build a complex cut through design.
You can also do the same with stars, polygon etc via the star tool. Go to the square star tool and create a square star and once you have that, change the number of points etc https://youtu.be/XWIlv3Hq3zs
You need to set the same blending mode for the layer as listed above and you will see the same punch through design (no matter how many layers you have) as long as they are below the vector.
The design is still live so you can modify the points as well as number of star points etc