There is no way to get a single download of all scripts. This has been broached in the past, and I don't see my past posts on it. Perhaps they were removed in the recent forum purging.
But the only way to get offline copies is either copy/paste into a text doc, or save a change to a script in the script editor which creates a temporary text copy of it in your Windows user AppData/Local folder under your world name. The copy there should be copied elsewhere, as the copy in that Local folder will be automatically deleted when the script change is submitted or abandoned in the script editor.