This new updates as follow: (4/25 3:00 pm.)
1. Optimization
Treasure editor:
1.) The default setting for new created item will be Rare;
2.) The existed items (non Rare) cannot be available to switch to Rare.
The Last Warlord Version Patch 142 Update Notice（V1.0.0.3407）
Source: Steam Community (opens in a new tab)