Reviving this thread to mention a workaround I found whereby you can load a gradient into affinity by first describing it in an SVG file.
So here goes:
1. Create an svg file using any text editor with your color stops (as hex colors, rgb does not appear to be supported) and their percentages as shown below:
<svg width="110" height="400" version="1.1" xmlns="http://www.w3.org/2000/svg">
<defs>
<linearGradient id="Gradient1" gradientUnits="objectBoundingBox" x1="0" x2="0" y1="0" y2="1">
<stop class="stop1" offset="0%" style="stop-color:#063168"/>
<stop class="stop2" offset="10%" style="stop-color:#1A5996"/>
<stop class="stop3" offset="20%" style="stop-color:#1886C2"/>
<stop class="stop4" offset="30%" style="stop-color:#54B3DE"/>
<stop class="stop5" offset="40%" style="stop-color:#C1D7EA"/>
<stop class="stop6" offset="50%" style="stop-color:#FFFFFF"/>
<stop class="stop7" offset="60%" style="stop-color:#FDC579"/>
<stop class="stop8" offset="70%" style="stop-color:#FA7C59"/>
<stop class="stop9" offset="80%" style="stop-color:#DA3C3A"/>
<stop class="stop10" offset="90%" style="stop-color:#9F1943"/>
<stop class="stop11" offset="100%" style="stop-color:#69012C"/>
</linearGradient>
</defs>
<rect x="5" y="5" width="90" height="390" fill="url(#Gradient1)"/>
</svg>
2. Open your svg in Affinity Designer (probably works in Affinity Photo too, but I haven't tried).
3. Select the rectangle, then go to the "Swatches" panel, click the "add fill to palette" button.
4. Now you can close/discard the svg file and use your freshly imported gradient in any other document by selecting it from your palette.
