How to add footnote/endnote that is a parenthetical thought rather than a citation of a source?
Use Word's insert footnote function. You can safely mix Word processor and Zotero generated footnotes (technically they are the same thing). You can't use Zotero's insert a citation feature since no citation is used, and you can't just use the prefix or suffix to do that.
Alternatively, you can edit the plaintext document after unlinking Zotero citation.
Research Rabbit is a free web-based literature mapping tool. It lets users find more relevant papers based on one or more seed papers.
To use Research Rabbit
All Citations
For citation styles, refer to Fondren's Citation Style Guides.
Below are just a few quick links.