The documentation for Qt::AA_DisableSessionManager on Qt Namespace page says that this value has been added in Qt 5.13. It seems to be wrong, this value is only present since Qt 5.14.
The simple proof is as follows: go to this page for Qt 5.13.2 and search for AA_DisableSessionManager -> nothing is found. But on this page for Qt 5.14.0 the value can actually be found.
I figured this issue out differently - tried to set this attribute and build with Qt 5.13.2 at AppVeyor CI, the error message was as follows:
..\bin\quentier\src\main.cpp(59): error C2039: 'AA_DisableSessionManager': is not a member of 'Qt'
c:\qt\5.13\msvc2017\include\qtcore\qstring.h(1859): note: see declaration of 'Qt'
..\bin\quentier\src\main.cpp(59): error C2065: 'AA_DisableSessionManager': undeclared identifier
Here is the review for the addition of AA_DisableSessionManager, just in case.