control the opening mode (offline) with sharepoint shortcut pointing at excel file (now enforce online)
in a document library, you can enforce the use of client application. so excel does open in excel offline. when creating a shortcut to file, it open online anyway.
I would like to be able to 'ban' online cause we use some project file maintained by lots of different people and i've noticed several cases of data loss due to version being ovewritten.