Previous issues had been opened for this but Firefox didn’t support changing them at the time. Firefox 60 will have support for extensions to change their shortcuts and it’d be great to be able to choose different keys for Bitwarden shortcuts like using ⌘+\ on macOS for those coming from 1Password.
This is currently working for me. Navigate to your addons/extensions options (about:addons), click the settings cog, and select “Manage Extension Shortcuts” from the dropdown menu. Bitwarden should be there.
Small bug: The “open sidebar” shortcut is not labeled.