From VFXPedia

Replacing Tools

To replace a tool, drag the new tool onto the flow from the bins or toolbar and place the mouse pointer directly over the tool to be replaced. When the mouse button is let go, a confirmation dialog will appear asking if the existing tool is to be replaced with the new tool.

If the new tool has settings that are identical to those in the original tool, these settings will be copied to the new tool. For example, replacing a transform tool with a merge will copy the existing center, angle values from the transform to the merge.