I an not too sure what linked columns are so can't comment but I have found a work around for multiple pages in designer.
Create a multiple page document and convert to pdf. You can do this in Word, etc. Open the file in Affinity Designer. Designer maintains the multipage of the original document.
I discovered by opening a document template, originally created in InDesign and exported as a pdf template. All layers etc. were retained. I have since check by creating a simple document in Word and saving as a pdf. My documents had two pages so not too sure what limits there might be.
It is working for me as a work around on a small document with tables , vector graphics and bitmaps and a lot of text. Obviously Publisher would be much better, when it arrives.