Hello,
I followed your tip I created a document 6 in. x 4.5 in. at 300dpi. I opened the resize dialog window changed the dpi to 150 with resample unchecked, the pixel/inch dimensions where grey and didn't change, I clicked the resize button. Once finished I reopened the resize document window and it now showed a 12 in. x 9 in. document at 150 dpi. This is what I was asking about in the first place.
That what I was expecting to happen, but because it wasn't updated while I was making the initial changes I didn't think/realize it was going to happen. The fact that I could not see the change in the dialog window prior to clicking "resize" is what caused the confusion so I didn't continue. It would be nice to see the change happen in the first window and not have to reopen a second window to know it had resized dimensionally.
I think you can understand my confusion when "However Affinity doesn't calculate or show this for you and the dimensions in the input box remain the same (even after you change them to a physical dimension). This again doesn't help much. " Because I never saw a change in the dialog window I was under the impression nothing was going to happen or change.
Maybe this is something that could be dealt with in future updates.