Doom placed normally on the agenda are all "in play", not just those littered on enemies and locations. (rule)

In Play and Out of Play

The cards that a player controls in his or her play area are considered in play.

The current act, the current agenda, each location in the play area, and each encounter card in a investigator's threat area or at a location, are all considered in play.

Out of play refers to the cards in a player's hand, in any deck, in any discard pile, in the victory display, and those that have been set aside and/or removed from the game.

A card enters play when it transitions from an out-of-play origin to an in play area. A card leaves play when it transitions from a in play area to an out-of-play destination. Tokens on in play cards are considered in play. Resources in each investigator's resource pool are also considered in play.

With one in play + other one in discard + other hand full, one can take 2 dmg and replay the other one to replace the damaged shield without the forced effect. This effectively gives 2hp for one click, which is not bad considering this combo is infinite and not using a card from hand.

It's an amazing pick for Dunwich Legacy to counter certain nasty treacheries and even final boss. You definitely should pick 2 copies for anyone who can have this card via deckbuilding options. You can even buy Versatile to have it on anyone. Even if it didn't find good usage during scenario, you still can submit it to skill test

It only checks 1 or more doom at the moment of attaching/swapping, so if you already managed to get 2 assets attached and then the agenda wipes off all the doom (one doom just does not count towards the threshold, but still in play and to be removed), now you can use clean assets that are already attached which could be handy in agenda with tight doom threshold.

Just played with it on the repackaged Carcosa. I see this card as a chance to include 4x Unexpected Courage but the 3rd and 4th copy will be underpowered. In practice you either cannot use it or get 2 icons. The benefit of this card is not the possibility to get 3+ icons, but to save deck space for flex character that needs a lot of non-skill cards after fully upgraded, so quite niche but at least I know when it is needed. (e.g. Only 2x Unexpected Courage and 2x "Not without a fight!" remains to make it the most almost-wild concentrated, ensuring that when you draw one, it better be multi-purpose.)

It feels similar to Rise to the Occasion, which need a complicated condition of character with low base but with some asset buffs on top to win the test with the +3 commit effect. And that one can only be committed to yourself as well.

A little tech is to make the lead investigator be someone with this card so there is a chance to draw enemy encounter and get engaged (or try forcing this with On the Hunt), and now you can commit this card to help investigators at the same location. One other tech I found is to find scenario Parley action that test , which you can ignore AoO. Finally when using Survival Instinct to get away from multiple enemies, that many enemies will help boost the success rate.