Hi and thanks for the review! If you have feature suggestions please report them to the GitHub issues page instead of here. :)

1. I think you are looking for the "Discard on open" checkbox that each search engine has in SSS. It avoids creating a new tab. You can already use engines like es:{searchTerms} for searching with the Everything app.

2. You'd have to use "file:///" before the actual path, but file paths won't work anyway because the WebExtensions API will block them as invalid URLs (i.e. "Error: Illegal URL: file:///C:/Applications/Something.exe") even though Firefox recognizes them as correct when writing them in the URL. ¯\_(ツ)_/¯

Cheers!