Hello! This is confusing - it confuses me too. As others have said, it impacts Coherency Toughness regen. The tooltips are not particularly clear and need some TLC (I’ve brought this up as an issue).
Generally, if it’s not linked to a specific action (e.g. you do X, you replenish Y Toughness), it’s only a bonus to the Toughness regen from Coherency.