When I install SingleFile and import the saved settings from Vivaldi, the settings stay there for a day or two, and then vanish. At that point, I have to uninstall the extension, reinstall it, then reimport the settings.
If I click the icon in the toolbar to save the current tab to SingleFile, it saves every tab, which means I need to open the tab in its own window before invoking SingleFile. If I fail to do this, Orion beachballs until every tab has been saved to a file. (With the Firefox version, at least, right-clicking on a page and invoking SingleFile from the context menu seems to behave correctly, and the toolbar button also behaves correctly after this has been done once. No idea if it'll stick, though…)
Both behaviours happen with the Firefox and Chrome versions of the extension.
0.99.131.0.2-beta (WebKit 621.1.2.111.4) BTW, it would really help if there was a "copy" button next to this in the About dialog…
macOS 14.7.4 (23H420)