Disband:

Learn about the Disband option for settlers in Sid Meier’s Civilization VII when cities pass level 9 to 10 and cannot replenish.

If all your cities have passed level 9 to 10, you can no longer replenish settlers. If you need to undo a settler, disbanding is the final option available. However, it is generally preferable to replenish or create a new city to keep your options open.

If the home city of the settler is happy enough and the settler is disbanded or replenished, a thanksgiving festival will occur for one turn, provided the city was not growing before this action.