Level Up is a RimWorld mod that notifies you when colonists level up.
Subscribe to the mod on Steam Workshop or download the latest release here and unzip in your Mods-folder.
Start the game and enable the mod in the Mod menu. Place it anywhere below Core and Harmony^1 in the load order.
You will automatically get notified whenever a colonist level up. Advanced configuration is available in the Mod settings.
This is caused by a mechanic in vanilla RimWorld known as skill decay. Skills at lvl 10 and higher lose xp. If xp goes low enough, the skill levels down. The rate of skill decay increases with every level - It is slow at lvl 10, and fast at lvl 20. This can lead to two problems:
A colonist on level 10 or higher in a skill she almost never uses will lead to that skill almost always ending up at the very top of lvl 9, because skill decay stops as soon as a skill goes below lvl 10. This means that only a tiny bit of xp is needed to level her up to lvl 10 again, which then goes down to 9 again, and so on.
A colonist with a high level skill she uses almost all the time will likewise lead to that skill jumping up and down between e.g. lvl 19 and 20.
Level Up has a cooldown between actions to make this feel less irritating, but it does not in any way prevent or slow down skill decay.
Pull requests are welcome, for both code and translations. Please open an issue first to discuss what you would like to change.