richardmtl

Initially I thought using XnView's Contact Sheet feature would be a good idea to produce at least a PDF. But for me it produces only broken PDFs on Windows. Maybe this is working for everybody else?

I doubt any route you take in Affinity Designer would be easy, obviously setting a document size and a grid to match would be a helper then...
Import the SVG’s in rows/columns, so if ten SVG’s fit a row, import ten SVG's Select the bottom SVG in the layer stack and place it at the first grid square on a row/column and the top SVG in the layer stack on the last grid square  Select all the SVG and use Auto distribute would seem the logical method. The Photo collage makers like TurboCollage don’t support vector files like SVG else it would have been a very simple job in that app.

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You can also use Layer > Create Compound - change the Curves layer to Subtract. You don’t need to change the Fillmode with this method, plus objects remain editable, such as you could rotate the curves layer.
 

Adding slightly to this, note that alternately you can Alt (Windows) or Option (Mac) click on the toolbar Subtract button to create the compound.

Hi! I realize this likely seems like a very basic question, but I can't seem to solve it. I want to use the fill tool to fill in several objects with white, that are currently black. Here's the flow I would expect:
 
1) Select Fill tool
2) Select the color I want to fill in the objects (actually, I'd look for an eye dropper tool but I haven't seen one, but since all I want is pure white, the eye-dropper isn't important at the moment)
3) Click on the object I want to make white
4) See the object change to white
 
Instead, what seems to be happening is, at step 3, the White that I had configured changes to Black (the color of the object), so I need to repeat step 2 again. I have many objects to fill, so the extra clicks are somewhat annoying.
 
What am I missing here? :)
 
Bonus: Is there an eye-dropper-type tool?