I really don't understand Affinity in this matter.....
When InDesign was released, Adobe ensured that users of QuarkXpress (the market leader at the time) could switch seamlessly.
After all, InDesign could simply open QuarkXpress files.
It is therefore a mystery to me that Affinity does not pay attention to this.
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I have been using Adobe software (InDesign, Illustrator and Photoshop) for more than 25 years.
I currently have a Creative Cloud All Apps agreement.
This means that I have literally thousands of files on my computer.
For InDesign these are all stored in the "indd" format. So not idml.....
Converting all my files to "idml" is impossible.
I think many people are in my situation.
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Using software from a third party (MarkZware) is not the right solution.
Affinity should address the solution by themself.