This mod is an unofficial port of Clear Despawn (Due to some strange new rules on CurseForge, I had to give it a new name instead of calling it Clear Despawn Unofficial).
It makes dropped items start flashing when they are about to despawn (default: 20 seconds remaining in 1.0.0).
The original flashing behavior seems too fast to be noticeable in 1.21, so some adjustments have been made, while maintaining a similar overall experience.
The mod is compatible with ItemPhysicsLite and Loot Beams: Refork. ↓↓

(1.0.0) You can customize its behavior via the DespawnNotifierConfig.toml file located in your config folder:
⏰Time for Flashing - The number of seconds the item has left before despawn to start flashing (default: 20)
⭐Whether to have item flash faster as it gets closer to despawning - (default: true)
(2.0.0)
⏳ itemFlashStartTimePercentage: The percentage of an item's total lifespan remaining at which it should begin flashing. For example, a value of 20 means items will start flashing when only 20% of their lifespan remains.
⚠️ isUrgentFlashEnabled: If enabled, items will flash faster as they get closer to despawning.
🚨 urgentFlashThresholdPercentage: If urgent flashing is enabled, this sets the threshold (as a percentage of total lifespan) below which urgent flashing kicks in.
✨ flashAlphaMin: Minimum alpha (transparency) value during the flash cycle. 0.0 = fully invisible, 1.0 = fully opaque.
💡 flashAlphaMax: Maximum alpha (transparency) value during the flash cycle.
🔁 flashCycleTicks: Duration in ticks for a full flash cycle. Lower values = faster flashing.