I think you only need a single preset for that. Why do you think you need 2 of them?
It was always the case on Windows; however, there is no any validation in the application for that so technically a user can set a partial preset as a default preset.
I cannot explain this behavior in DxO PhotoLab 4 for macOS. For me it looks like a bug there.
Alex
Because…
As is the case for PL3 for Mac.
Remember, this has only become a problem in PL4 for Mac. So, yes, I would say it is definitely a bug.
Do I need to report it officially or has it already been noted from these discussions?
If you apply a full preset with a disabled tone curve, you should get what you need.
I’m not responsible for DxO PhotoLab for macOS development so I don’t take any notes for it. You should report it officially.
Alex
OK. Here’s what happens…
Here’s the preset in the editor
Here’s the tone curve edited as it looks after editing it for an image
Here’s the tone curve after having applied the “full” preset (with the disabled tone curve)
As you can see, it obliterates the previous edit.
Which is why I ended up creating two presets 
I’m sorry to appear dumb but how do I do that for non-beta issues?
This is completely unexpected to me. Did you create your preset that is being edited from a full preset?
You can contact directly @akarlovsky and @SebinParis who are responsible for QA for DxO PhotoLab for macOS.
Alex
I had to create it from a full preset because it is impossible to add the tone curve to an empty preset or, in fact, to any preset that doesn’t already contain the tone curve.
Many thanks. Maybe it’s best if I signal them to this thread in a DM.
That’s the best way to demonstrate the bug. I just tried that and saw the 6502 value. Also PL4 crashed when I tried to edit the tone curve.
Thank you Calle for your video. Its the first time, I do understand now, what this discussion is about And can confirm, the same for me on latest Catalina with latest PL4.1.1. But for me it doesn’t matter, because it’s not my kind of workflow. But understand it could be annoying.
Nevertheless, DPL lets me select any preset for default, be the preset provided or self-made, a full or a partial preset. I propose that DxO limit the eligibility of presets for default and comment it, be it as a comment in the settings or as a popup.
Your statement provokes a few questions too:
Just ran a quick test.
Leaving any tool in a preset but not active, reverts the setting for that tool when the preset is applied.
I thought the whole premise of partial presets was that they only touched those tools that are selected as part of the preset.
So far, I have not been able to find any other tool that fails to cooperate with being used in both full and partial presets. It seems to be solely the tone curve in PL4 on a Mac that refuses to play nicely.
found the same thing.
And why not use a partial preset as default?
Imagine you just want to add a watermark as partial preset and use it for default. What’s wrong about that?
Seems it works as expected. No?
Alex
I agree that users should not care about whether a full or a partial preset is set as default in the application preferences. I would consider this as a bug.
If a default value of a correction doesn’t affect an image, then active \ inactive state doesn’t change anything.
None as I’m aware of.
Alex
The architecture of the application requires all settings to be associated with an image, even if they all are inactive and do not affect an image in any way. But it’s an implementation detail that should not disturb you.
Alex
Well yes but that is the problem with trying to use a full preset for partial preset work. It does too much.
Excellent, so we can expect a fix tomorrow? 
I don’t understand why you want to convert a full preset into a partial preset.
Sure! As soon as you confirm that you’d switched to the Windows platform
Alex
This all started when I was helping someone in these forums to create a preset, based on the DxO Optical corrections only preset. Why? Because the aspect ratio isn’t checked in the distortion tool and that was important for his lens.
Because he wanted to be able to apply it retrospectively, I copied the DxO preset and unchecked everything else, to make a partial preset.
That worked fine as long as you had already used a full preset to start with.
I also wanted to use the same preset for both retrospective changes and as a default as well.
Which is where this whole sorry saga began
Yeah, right. I started with Windows 3.0 and finally broke free at the time of Windows XP, when I was heavily involved in C# programming of a massive business management application.
My old Dell laptop was showing its age and a good friend suggested that a 17" MacBook Pro cost less than a Windows equivalent. So, I installed Parallels and XP and there was simply no going back.
After a while, I discovered that Xcode was free and so I started developing for OS X and iOS.
Yes, Objective-C and manual reference counting weren’t much fun but things soon changed and now we have Swift, which is far more interesting.
Nowadays I would struggle to find my way around Windows
You could simply edit the default “Optical corrections only” preset with a new correction key for the distortion’s aspect ratio 
I think that C# and Swift are on pair regarding being interesting. You probably know that DxO PhotoLab for Windows is mainly written in C#.
We don’t have the bug with the Tone curve correction in DxO PhotoLab 4.1 for Windows. Isn’t it enough for you? 
Alex
Windows 10 is easy to navigate. Even a Mac user could do it.
Mark