Harvest With

The Harvest with window sets up a hotbar slot that aims a tool at a kind of resource, such as a pickaxe at ore. The first row holds the tool. The rows under it list what that tool can gather, and a tick marks the one the slot aims at.

Until a tool is chosen, the first row reads "Drop a tool here" and no resources are listed.

Harvest With, pickaxe — The window open on a slot that mines with a pickaxe. The first row holds the pickaxe. Under it are Ore, Sand and Digging Graves, and Ore is ticked.

Opening it

Shift+right-click a hotbar slot that holds the harvest action, and choose Edit Item.
Right-click the window to close it.

Using it

Drop a tool on the first row to bind the tool to the slot. The slot then aims at the first resource that the tool can gather.
Click a resource to aim the slot at it. The tick moves to that row.
Hover over the first row to read how to set the tool.
Right-click the window or a row to close it.
Drag the window to move it. With the Lock the layout setting on, it stays where it is.
Drag the corner grip to resize the window.
Roll the mouse wheel over the rows to scroll them.