You cannot manually save in Kingdom Come: Deliverance. However, there are some items and mechanics that allow you to save at certain points during the game.
- The game will save when you start a new quest or reach some specific milestone in the quest.
- Using any service in a bathhouse will save your game
- Purchase or brew a Saviour Schnapps and drink it. You can buy Saviour Schnapps in taverns and its the closest thing to a manual save.