I've been playing Warframe for about 10 years, and I have a ton of vaulted relics. I don't want to waste them when farming for void traces, etc.; I would like to save them for a radshare group. Currently, there is no way to distinguish vaulted from non-vaulted relics when choosing them mid-match (defense, survival, etc.), so I have a hand-written list of allowable relics next to me at all times. I believe this could be made easier for everyone with a simple symbol!
There are already many symbols on Warframes and weapons indicating number of forma used, archon shards attached, whether or not it has been subsumed, etc., so I think it would be great if relics had a "vaulted" symbol on them as well.