Why is Audition CC 2019 (a.k.a. 12.x) is missing from Thor (a.k.a. Creative Cloud Desktop)? The installed Adobe Audition CC is 2018, Build 11.1.1.3., on Windows 7 SP1 x64 Ultimate, with the latest Creative Cloud Desktop version (4.8.1.435).
Before the Creative Cloud Desktop update last week that removed all except the last ~two versions from their servers, I had the same issue:
To access the other versions' menu:


