Here is a video of using the Rotate tool to rotate a dart. To select multiple points in the Rotate tool, hold down the Ctrl key. When you have selected points press Enter. (One point will appear to remain selected after pressing Enter.) Select the dart point as the origin of rotation (or other point for rotation - for example, sometimes the bust point is not used as the dart point so in that case select the dart point as origin.) For the angle, you don’t have to type in (AngleLine_P1_P2 - AngleLine_P3_P4), you can select both angle of lines in the f(x) dialog, but I wanted everyone to be familiar with this naming convention for an angle of a line.
Also, it’s a good idea to direct the lines of the dart so that the 1st point is the dart center point and the 2nd point is the dart leg point, in case you need to rotate the dart in the future.