Copy-Paste a file by Ctrl+C -> Ctrl+V
Like in almost ALL Windows apps, also in the Teams app, the good-old universal "Ctrl+C -> Ctrl+V" keyboard feature should be introduced to copy-paste files!
These are sadly not as universal as Ctrl+Insert -> Shift+Insert (old DOS/Windows short-cuts). This works across most apps and OS. Please enable these short-cuts in Teams.