pyRevit

Code
Library
Unhide All Elements in View
# -*- coding: utf-8 -*-
from Autodesk.Revit.DB import *
# .NET Imports
import os, clr
clr.AddReference("System")
from System.Collections.Generic import List
# ╦ ╦╔═╗╦═╗╦╔═╗╔╗ ╦ ╔═╗╔═╗
# ╚╗╔╝╠═╣╠╦╝║╠═╣╠╩╗║ ║╣ ╚═╗
# ╚╝ ╩ ╩╩╚═╩╩ ╩╚═╝╩═╝╚═╝╚═╝ VARIABLES
# ==================================================
doc = __revit__.ActiveUIDocument.Document
# ╔╦╗╔═╗╦╔╗╔
# ║║║╠═╣║║║║
# ╩ ╩╩ ╩╩╝╚╝ MAIN
# ==================================================
if __name__ == '__main__':
all_elements = FilteredElementCollector(doc).WhereElementIsNotElementType().ToElementIds()
unhide_elements = List[ElementId](all_elements)
with Transaction(doc,__title__) as t:
t.Start()
doc.ActiveView.UnhideElements(unhide_elements)
t.Commit()

⌨️ Happy Coding!
Erik Frits