Thanks for the info. I can see the window drop menu but it seems only working when files are first opened via the "open (file) in new window". Then I can choose another view in the dropdown menu..
Opening several files in the same window only works via File > open file in new window or Open (yellow map icon) > open in new window. This seems to be the only way for opening several files in one window.
Once opened you can choose another window view (tile horizontal, tile vertical, cascade and autoarrange).
Manually resizing works now when selecting minimize or maximize button for files.
Momentarily I'm using Wavepad version 8.23. My first version was 7.14. The older version I used had another layout and seemed easier to find the windows option.