Hello,
I would capture all sessions of all session types in the history section.
In short I would get all sessions I can see when I go under the Jobs node with all the infos about session type, end time, session name, etc.
Get-VBRBackupSessions is limited because I can't get the plugins and agent sessions
You'll need to use the job type-specific session cmdlets i.e. Get-VBRComputerBackupJobSession, Get-VBRNASBackupSession (though it appears NAS sessions also appear with Get-VBRBackupSession), Get-VBRPluginBackupSession, etc.