Logging

normal logging.

        Debug.Log("LOG!");
        Debug.LogFormat("LOG! (normal){0}", 1 + 1);     // LOG! (normal)2
        Debug.Log($"LOG! (zero padding3){1 + 1:000}");  // LOG! (zero padding3)002

        // WARNING
        Debug.LogWarning("WAR!");
        string aaa = "a";
        Debug.LogWarningFormat("WAR! (space padding5){0, 5}x", aaa);  // WAR! (space padding5)    ax
        Debug.LogWarning($"WAR! (space padding5){aaa, -5}x");         // WAR! (space padding5)a    x

        // ERROR
        Debug.LogError("ERR!");
        Debug.LogError(string.Format("ERR! (bracket){{{0}}}", 0.25));  // ERR! (bracket){0.25}
        Debug.LogError($"ERR! (bracket){{{0.25}}}");

object specific (click the log message in console, specific object marked)

        // Object specific
        Debug.Log("message for this object", this);
        Debug.Log("message for other object", other);

log file

C:\Users\[UserName]\AppData\Local\Unity\Editor\Editor.log

Gizmo

draw original gizmo

set Script which has [OnDrawGizmosSelected] method (like below), and then select the Object.

private void OnDrawGizmosSelected()
{
    Vector3 fromPoint = Object1.transform.position;
    Vector3 toPoint = Object2.transform.position;

    // Draw Line
    Gizmos.color = Color.yellow;    // color select
    Gizmos.DrawLine(fromPoint, toPoint);

    // Draw Wire Sphere
    float radius = 3.0f;
    Gizmos.color = Color.green;    // color select
    Gizmos.DrawWireSphere(fromPoint, radius);

    // Draw Sphere
    Gizmos.color = Color.red;    // color select
    Gizmos.DrawSphere((fromPoint+toPoint)/2, 0.5f);
}

images/unity/debug_gizmo_draw.jpg