Is there a way to change the style of all scrollbars (Win10)?
Is there a way (API, dlls, msstyles ...) to modify the style (remove some elemets, change colors, width, ...) of all scrollbars that appear in Windows 10?
For example from this 
to this 
Answer
You don't need to write a program if you want to change all scrollbars on your system. In fact, it would be a colossal undertaking to do so. You would have to hook the Windows API functions that are responsible for drawing scrollbars and replace them with your own drawing code. Aside from the fact that an advanced understanding of Win32 programming will be required (far more than anyone can teach you in a single Stack Overflow answer), it will be extremely difficult to ensure that your code behaves identically to the original. Application bugs are inevitable, even after lots of testing. No user who cares about the stability of their system will want to run such an application.
From your screenshot, it looks like you just want to change the width/height of the scrollbars to make them smaller. Although the UI for customizing advanced Appearance properties has been removed from Windows 8 and later versions, the metrics can be set manually in the registry. Scrollbar size is among them.
- Navigate to the following registry key:
HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics - Set the
ScrollWidthandScrollHeightvalues to your desired size in pixels, multiplied by -15.
For example, to set your scrollbars to only 8 pixels, you would set the values to -120. (This is the smallest that you can go.) The default value is -255. - Restart your computer to ensure that the changes take effect.
If you aren't comfortable modifying the registry, you can use a third-party application to do it for you, such as Winaero Tweaker.
Be forewarned, however, that compatibility problems are not to be unexpected with either of these solutions. If the Windows team intended to support custom-sized scrollbars, they would have left the Appearance customization interface intact.