I dont who fixed what, but the bitwarden sidebar button is back!

Version 1.52.0 by bitwarden
Version:79.0.4143.22 (x86_64) Opera

@akramipro: I have the same issue here on an intel Mac Pro

Version:78.0.4093.147 (x86_64)
Opera is up to date
Update stream:Stable
System:macOS Version 11.5.1 (Build 20G80) 11.5.1 x86_64