I'm glad you like the extension! Extensions can only add a single top-level context menu item, but you could disable the rest of the search engines from the extension's options to search with your preferred engine from the context menu, without having to open a submenu. The drawback is that the "Open image" tool would no longer be accessible from the context menu and the browser toolbar.

If you have more than one engine enabled, and you would like to initiate a search with all of them from a top-level context menu item, you could also set the "Search all engines" option to "From context menu". That way the rest of the features would still remain accessible from the browser toolbar popup.

The legacy Google service is still available in the extension, now listed as Google Images (deprecated), but it only works for some users, you can enable it from the extension's options. People in the EU have had some luck restoring access to the service by using a Google account and following this guide: https://github.com/dessant/search-by-image/issues/309.