Replace All in Tabs v1.0.9resigned1
The default behavior for "Open all in Tabs" is to add new tabs to the existing tabs. There used to be an option (browser.tabs.loadFolderAndReplace) to replace all existing tabs with the new ones, but that was unceremoniously removed.
The Tab Replace addon added this ability back, but Quantum broke it.
This new version uses web-extensions, but unfortunately, it can only be added to the right click context menu. You cannot override the "Open all in Tabs" behavior, nor can you add anything to the left click menu using web-extensions.
If you want this extension to work better, please vote up bug 1448518.