Are you sure you had your "Programs and Features" sorted by name?
If it is complaining about "Microsoft Visual C++ 2015 Redistributable (x64)" (not "Studio" in this name) being installed already we should be able to see it in your list somewhere above "Microsoft Visual Studio ..."
However, with the current version of VS Code you should try to install `Microsoft Visual C++ 2017 Redistributable (x64)" (providing you are running a 64 bit Windows - otherwise you may want to opt for 32 bit across the board.
But to get official help for Particle Workbench can you follow the steps in this thread
@m_m and team will then have the data they need to properly assist.