PF> I may be missing something, but I just installed v.1715 and the IF noise reduction menu looks exactly the same as in 1710 and previous. It doesn't have any of that "Custom", etc.
In either the Audio Noise Reduction or IF Noise Reduction pull down menus and just under those you will have a label titled 'Profile'. Click on the pull down arrow button & you will be presented with 5 different profiles starting
with HiFI & ending with Custom. When you hit 'Custom' you will be presented with many slider controls to play with to your hearts content.
The Custom controls do differ a little to much earlier SDR# releases. eg 'quality' slider control gone, but new is the 'slope' control.
The "new algorithm" is part of the recent SDR# releases program code.
Hope that helps.