As of this moment, the answer is plain and simple - NO.
It is understandable to implement this feature is a bit tricky, but it's a long time since Windows 10 Beta and the launch. The following is credited to be a direct quote from Microsoft developers over the scaling issue sourced from here.
"Scaling is a complex problem for the open Windows ecosystem, which has to support devices ranging in size from roughly 4” to 84,” with densities ranging from 50DPI to 500DPI. In Windows 10 we took steps to consolidate and simplify our developer story for scaling and to improve the end-user visual experience. Stay tuned for future release!"
Now let's move to the official Microsoft help page, in this case their Technet magazine tip on how to Fix Scaling Issues on Windows 7
If you’ve enabled scaling and the text in an application is blurred or unreadable, you may want to disable display scaling for that particular application. To do this, right-click the application’s shortcut and then click Properties. On the Compatibility tab, select Disable Display Scaling On High DPI Settings, and then click OK.
Alright, now we've seen the older help page, let's see Windows 10 version of fixing the scaling issues on their help page. I really want to quote the entire page here, it's just that hilarious, but I'll let you construe the entirety of it. I'll just quote Solution 2:
You can disable display scaling for an individual desktop app in Windows 10. Here’s how:
Step 1: Select the search box in the taskbar, enter run programs, and
then select Run programs made for previous versions of Windows in the
search results.
Step 2: In the Program Compatibility Troubleshooter, select Next.
Step 3: Select your program from the list, and then select Next.
Step 4: Select Troubleshoot program, select The program opens but
doesn’t display correctly, and then select Next.
Step 5: Select Program does not display properly when large scale
font settings are selected, and then select Next.
Step 6: Select Test the Program to open the app with the new
settings. If it works, select Next and save the settings. Otherwise,
select Cancel.
Unsurprisingly, all these steps ever achieve is to Disable Display Scaling On High DPI. The same which was mentioned earlier in the windows 7 solution.
So, it is now clear that there is no possibility to change scaling per application, unless it's developer implements it as a DPI-aware desktop or win32 application.
Since we have no official confirmation, it is not clear if this feature will be implemented within Windows in the foreseeable future.
Best Answer
The issues are mostly solved now, after a cumulative update of Windows 10 released around 10 or 12 August 2016.
Everything looks perfect on my laptop's 3K display, and although I still feel like the text is sometimes slightly blurry on my external Full HD screen, it is much more crisp and readable, and the icons now look all right!