1. Open the menu of a lane by clicking on the menu icon (3 vertical dots).

2. Enter edit mode by clicking on the pencil edit icon.

3. Click on the    button* 

4. Search for a user from the search window that pops up.

5. Select a user and click 

The leader should now be set to the selected user.

*Note: Owner permission on the Board or Lane level is required to set or change a lane leader. If you do not have the appropriate permission you will not see the "Set Leader" button.