And now I've got another issue 

The option "Show arduino core and library sources" seems very useful - it shows my custom libraries and I have quick access to them. The problem is found when I compile a project. One of my custom libraries (RTC module class) uses Arduino Wire.h library for data exchange. And even if my this custom library is not used in .ino file - the compiler throws an error forcing me to include "Wire.h" to the .ino file (so, if I do this, compilation goes fine). On the other hand if I click "Show arduino core and library sources" again to hide libraries files in Solution Explorer tab - the compilation is successfull too even without including "Wire.h" to .ino file.

Is there a solution for this or I'm understanding or doing smth wrong?

Yes, I remember that I need to #include library (lib1, for example) into main .ino file, if it is used in another library (lib2). This applies to the library lib2, that is used in the main .ino file, as I understand. So I will need to #include lib2 as well as lib1. But in my case none of lib1 and lib2 is being used in the main .ino file, and the compiler asks me to #include lib1. That is the question. If I click again to "Show arduino core and library sources", then files are hidden in Solution Explorer tree and the compilation succeeds.

As far as I understand, it happens, because all files in "_libraries" section are being compiled regardless if they are used in the .ino file. 

But the way, I use v2 library format, as we discussed in this topic. I have a set of my custom libraries (GPin, GLED and so on) stored in one folder (GLibs), which is placed in Libraries folder. That is why (I think) VM shows all of them in Solution Explorer tree in "_libraries" section when I click "Show arduino core and library sources", even if they are not used in the main .ino file.