Temporary reference repository

I am writing a paper for which I will be consulting many potential references while reviewing the literature but using only a subset in the final product.  I am looking for a way to keep track of which references I consulted but rejected so I won’t waste time checking them again in a month or two.  I do not want to import references that I decided not to use into my EndNote library - note that this is a discipline for which a vast number of potential references exists. 

The only method I’ve been able to come up with would be to turn off “Sync” for the duration of the project, import the rejected potential references into EndNote Online and delete them when I am finished with the project.  I’m wondering if there is anything less kludgy. 

I saw a similar question in the past, and one of the respondents insisted that it would be worthwhile to import all the rejected references into the library.  No, that would not be worthwhile, so I am looking for other suggestions. Perhaps, though, I will have to resort to a spreadsheet…

Thank you in advance.

I fail to see why you wouldn’t want to incorporate them into a library. 

Since Endnote will only sync one library anyway, you could keep an endnote library of downloaded references on your desktop, and copy those you would like to keep, incorporate in your main synced library? In this way, when you were identifying new possible sources, if you export them to a temporary library, you can import them into the evaluated library and toss duplicates, so only new papers are there.  You could have two (or more) groups in the non-synced library, – those you have already copied, those that have been rejected, leaving those that have not yet been evaluated in the unfiled group.  New imported sources would default into the unfiled group, giving you a good way to keep them, separated.