Using the spline tool as a leader for dimension text offset or as an arrow for annotation on details, sections, elevations, interior elevations, or plan elements can be an effective method if used properly. If used improperly it creates a nuisance to clean up later. The spline should start from the text box in a horizontal direction, not angled up or down; from here it can make one or more bends to get to the arrow head that the text is associated with.
Below is an example of what the text/spline relationship should NOT look like:
This will turn on the spline handles as a non-print (view only) element. Drag the handles to start directly horizontal from the spline origin at the text:
These handles are available without the on-screen view options set to show spline handles, but they will only be visible/accessible if the spline is selected and will show as a faint green editing handle.
To ensure that splines are tangential when first placed set your spline options to “Natural” in the spline or info box settings. The following examples were all traced from the same 6 points, but only the Natural setting creates a consistently tangential curve: