MICROSOFT EDGE INSTALLER RUNNING UPDATE
Should Mozilla have let Firefox 57 (the new "Quantum" version), run alongside Firefox 56 after the update installed? What a mess that would be. Alas, Microsoft has always been overly sensitive to legacy concerns. Once installed, the new version of Edge should completely replace and override the old version in every case, with no workaround. There ought to be no way at all of running both of these side by side.
Given this, I expect a simpler solution for consumers to appear as well, so stay tuned. And any sites that were pinned to Start or the taskbar for Microsoft Edge Legacy will be migrated to the new Edge. You’ll have to re-pin Microsoft Edge Legacy to Start or the taskbar. For example, you’ll need to run the new Edge installer again before you can both versions side-by-side. If you don’t do it ahead of time, you’ll have a few issues to deal with. Microsoft also notes that the Allow Microsoft Edge Side by Side browser experience should be enabled before the new version of Microsoft Edge is deployed for the best experience. To enable this, open the Group Policy Editor, navigate to Computer Configuration > Administrative Templates > Microsoft Edge Update > Applications and select “Allow Microsoft Edge Side by Side browser experience.” Then, click the Edit policy setting link, and in the window that opens, select Enabled and then click OK. “If you want to let your users to see both versions of Microsoft Edge side-by-side in Windows, you can enable this experience by setting the Allow Microsoft Edge Side by Side browser experience group policy to ‘Enabled’.” “Installing the Stable channel of the next version of Microsoft Edge at system-level will cause the current version (Microsoft Edge Legacy) to be hidden,” the support document notes. (There are Registry-based workarounds, of course, so I’m sure we’ll find out what that is before the new Edge launches.)
The bad news? It requires it requires Group Policy, which leaves out Windows 10 Home users. A Microsoft support document explains how you’ll be able to run the old Edge and the new Edge together if you want.