The distance between the arrows depends on the FE mesh. It cannot be changed in the Display Properties.
The calculation provides a result value in each FE mesh node, so that in each FE node there is also a value of the line support and therefore, also a support arrow.
You can only change the interval between the arrows by means of the target length of the FE elements. To do this, use the drop-down menu Calculation → FE Mesh Settings.