private List<BaseEntity> Paste(ICollection<Dictionary<string, object>> entities, Dictionary<string, object> protocol, Vector3 startPos, BasePlayer player, bool stability, float RotationCorrection, float heightAdj, bool auth)
​

return pasteData.PastedEntities;​

it will be easier to use with callbacks, mentioned not all methods, i think u got the idea:

        private object TryPaste(Vector3 startPos, string filename, BasePlayer player, float RotationCorrection, string[] args, bool autoHeight = true, Action callback = null)
        {
...
Paste(preloadData, protocol, startPos, player, stability, RotationCorrection, autoHeight ? heightAdj : 0, auth, callback );
            return true;
        }

        private void Paste(ICollection<Dictionary<string, object>> entities, Dictionary<string, object> protocol, Vector3 startPos, BasePlayer player, bool stability, 
float RotationCorrection, float heightAdj, bool auth, Action callback = null)
{
...
      NextTick(() => PasteLoop(pasteData,callback ));
}

  private void PasteLoop(PasteData pasteData, Action callback = null)
{
...
   if (callback != null)
     callback.Invoke();
}

and for pasting data maybe you prefer to use something like this, idk how it would be better to implement yield in coroutine, maybe other way...

 ServerMgr.Instance.StartCoroutine(PasteLoop(PasteData pasteData, callback));

        public IEnumerator PasteLoop(PasteData pasteData, Action callback = null)
        {
            for (...)
            {
                DOSOMETING();
                yield return new WaitForEndOfFrame();
            }
        }