Similar to how it works in the Power of Chaos games, when you mouse over an equip spell/trap card or a monster that is equipped with such card(s), it shows the “equip spell card” symbol ontop of the relevant card.
This should also work for cards that are not strictly equip, but affect the card in some way - for example Call of the Haunted, Spellbinding Circle, Nightmare Wheel, etc.
So for example, if a monster is “equipped” by Spellbinding Circle, when hovering over the monster, it would show the equip sign ontop of Spellbinding Circle, and when hovering over Spellbinding Circle, it should show the sign ontop of the monster it affects.