The game itself is pretty charming and satisfying, but I find the "lock task" feature kinda janky.
I think the intended way to use it is just to have a farmhand doing the same thing in a 5 by 5 area. It's not very cost-effective since they will be idling for most of the time, but at least no repetitive input is required.
What's weird, though, is that I can cancel a locked task. Doing so will make the canceled farmhand doing the next available task in the queue. However, the icon of the locked task is still there, and when the farmhand finished their new job, they don't go back doing their original, locked one, and neither the icon for the original task nor the one for the new task will disappear.