Script Lab states in the description, that it works also with Office Online. How does that work? In Office Online I don't see any possibilities to add the Script Lab app (https://www.office.com/apps):
The above question leads to the two follow-up questions:
Can the Office JavaScript API be used without an AddIn?
If it is possible to use Script Lab (respectively, using the Office JavaScript API) for Office Online, I assume it must be possible to use the JavaScript API on a website to interact with a Word Online document (loaded into an iFrame) without having to install an Office AddIn? Would it be possible when hosting Office Online yourself using an Office Online Server (OOS)?
Can an Office AddIn have dynamic code like Script Lab?
If it is possible for Script Lab to dynamically change its functionality (by editing the JavaScript API code), is it also possible to create an AddIn that dynamically can update its content or functionality automatically (similar to the smooth update mechanism from ElectronJS)?
I did it this way. On the Word Online ribbon, navigate Insert | Add-ins | Store. Then enter Script Lab in the search. Then click Add by Script Lab item.
UPDATE 9/9/20: It is not possible to use the Office JavaScript library outside of an Office Add-in. It needs that context to initialize.