How can you add a new word to a search saved as collection? This collection is dynamic?
In Windows Scriv, I pull up the saved search and modify the search terms. That’s it. Scrivener will revise the search results and save the search term modifications automatically.
In the Windows manual, this is described in section 10.2.4 Saved Search Result Collections, under “Updating the Saved Search Query”.
As a special note, the Windows version doesn’t currently work correctly, in that it is supposed to be a little more difficult to mess up (depending on how you look at it) your search collection settings. Right now, indeed, you can open the collection, then open the search tool, type, and it’s modified (lost forever, again depending on how you look at it).
You are supposed to have to click a button to actually do that though, where the moment you type it flips over to the main Search Results tab. Thus that should change in the future. Keep an eye out in the “What’s New” appendix for each update. Notable changes that would alter how you’ve used the software, even if it is to fix bugs and missing features, often appear here.