Steps
On your workspace dashboard, locate the board you want to move
Click on three dot at right top corner of the selected board to open the context menu
Select "Move to" from the menu
A dropdown will show available folders
You can move it back anytime using the same method
Notes
Moving boards doesn't affect sharing or permissions
You can move multiple boards at once by selecting them with checkboxes
Moving a board to a new folder doesn't delete the original
Archived boards can also be moved between folders