I need to export designs as SVG so that they could be used in a web UI at a specific size (150 x 150 px). By this I mean that the graphic sits in a transparent space of those dimensions. However, even if I create a canvas with those dimensions and select to export the entire document, the SVG I get have dimensions that are based only on the space occupied by the objects inside the canvas and not including the clear space they sit in. I even tried making a rectangle in the background that's 150x150 px and setting opacity to 0% without luck.
In AdobeXD, for example, I can create an artboard that's 150x150px and export it with the resulting SVG being exactly the way I need it to be.
How can I do this in Affinity Designer? I'd like to create all of my SVGs in AD.