Пользуюсь так-же CoolSoft NSIS Dialog Designer:
1. Запустим CoolSoft NSIS Dialog Designer:
https://i.ibb.co/S0j3FJr/coolsoft-nsis-dialog-designer-01-14-09-20-09-2021-min.jpg

2. В настройках выберем путь NSIS в NSIS enviroment base path, у меня он находится C:\Program Files (x86)\NSIS:
https://i.ibb.co/pfYfhY7/coolsoft-nsis-dialog-designer-02-14-09-28-09-2021-min.jpg

3. Запустим:
https://i.ibb.co/3FpZS5v/coolsoft-nsis-dialog-designer-03-14-10-28-09-2021-min.jpg

Код:

Код:
; =========================================================
; This file was generated by NSISDialogDesigner 1.5.0.0
;
; Do not edit it manually, use NSISDialogDesigner instead!
; =========================================================

; handle variables
Var hCtl_test
Var hCtl_test_Button1
Var hCtl_test_Label1


; dialog create function
Function fnc_test_Create
  
  ; === test (type: Dialog) ===
  nsDialogs::Create 1018
  Pop $hCtl_test
  ${If} $hCtl_test == error
    Abort
  ${EndIf}
  !insertmacro MUI_HEADER_TEXT "Hello" "Hello"
  
  ; === Button1 (type: Button) ===
  ${NSD_CreateButton} 16u 30u 53u 14u "Click me!"
  Pop $hCtl_test_Button1
  
  ; === Label1 (type: Label) ===
  ${NSD_CreateLabel} 15u 9u 68u 11u "My Installer Test"
  Pop $hCtl_test_Label1
  
FunctionEnd

; dialog show function
Function fnc_test_Show
  Call fnc_test_Create
  nsDialogs::Show
FunctionEnd