customize share panel in Window OS
I have created a share source application in UWP window with the following source - see here on Github.
I want to share an image to Facebook and Instagram only through OS but share panel shows multiple application which I don't require. Is there some way to customize the share panel?
No, this is a system based dialog that always displays all options available to the user based on the type of content you are sharing (DataPackage). If you want to offer just the two mentioned apps, you will probably have to implement sharing manually (along with Facebook and Instagram login, etc.).
However, even though you don't require displaying the other apps, you might want to consider just keeping the default system UI, because it gives the users a wider choice, which is always a good thing. If the user does not have Facebook or Instagram, she would be unable to share the content, which is arguably worse than showing more apps than you require.