These details stolen from this February 2020 post over at ghacks.net.
You can generate this list yourself by entering edge://edge-urls into Microsoft Edge.
edge://about — Same as edge://edge-urls/
edge://accessibility — Inspect the representation of accessibility in Edge and modify accessibility modes.
edge://appcache-internals — Lists information about the application cache (that sites may use).
edge://application-guard-internals — returns the status of the Windows-specific Application Guard feature, host information, a log, and utilities to check URL trust, Ping, and more.
edge://apps — Lists all applications installed in Microsoft Edge.
edge://autofill-internals — Lists captured autofill logs.
edge://blob-internals — Lists blob data if available.
edge://bluetooth-internals — Provides information on Bluetooth connectivity including available adapters, devices, and debug logs.
edge://compat — Compatibility hub that lists Enterprise Mode Site List entries, User agent overrides, CDM overrides, and the status of Internet Explorer mode (including diagnostics).
edge://components — Installed plugins and components. The Adobe Flash Player version is listed here if installed, as is the Widevine Content Decryption Module, Trust Protection Lists, and other components.
edge://conflicts — The page lists all modules loaded in the browser and rendered processes, and modules registered to load at a later point in time.
edge://crashes — Lists all recently reported crashes. Includes option to clear the listing.
edge://credits — Lists credits for various components and features that Edge uses.
edge://data-viewer — Linked to diagnostic data.
edge://device-log — Provides device information, e.g. events of Bluetooth or USB devices.
edge://discards — Tabs may be discarded by the browser, e.g. to free up memory. The page lists those tabs and related information.
edge://download-internals — Displays the download status, and provides options to start a download.
edge://downloads — Opens the internal downloads management page listing all downloads of Edge.
edge://edge-urls — Lists all internal URLs.
edge://extensions — Lists all installed extensions and their status.
edge://favorites — Lists all bookmarks.
edge://flags — Opens a page full of experimental features that may be managed from that page.
edge://gpu — Provides detailed information about the capabilities of the graphics adapter as well as driver bug workarounds and potential problems.
edge://help — Displays the current version of Microsoft Edge and runs a check for updates.
edge://histograms — Stats accumulated from browser startup to previous page load.
edge://history — Opens the browsing history.
edge://indexeddb-internals — Information about the use of IndexedDB by sites.
edge://inspect — Configure port forwarding for USB devices and configure network targets.
edge://interstitials — The page displays various interstitial pages that EDge displays, e.g. when it detects a captive portal, on SSL errors, or when you are encountering lookalike URLs.
edge://interventions-internals — Lists the intervention status, flags, logs, and other information.
edge://invalidations — Lists invalidations debug information
edge://local-state — JSON data that lists browser features and policies, and their status.
edge://management — Page is only active if Edge is managed by a company or organization.
edge://media-engagement — Lists media engagement values, and displays sessions.
edge://media-internals — Provides media information.
edge://nacl — Displays NaCl (Native Client) information.
edge://net-export — Option to capture a network log.
edge://net-internals — Removed.
edge://network-error — Removed.
edge://network-errors — Lists all available network errors that Edge may throw
edge://new-tab-page — Opens a blank New Tab page.
edge://newtab — Opens Edge’s default New Tab page.
edge://ntp-tiles-internals — Provides information on New Tab Page data, e.g. whether Top Sites is enabled, the list of sites, and more.
edge://omnibox — Displays address bar input results on the page.
edge://password-manager-internals — Provides internal information on the password manager in Edge.
edge://policy — Lists policies that are set in Microsoft Edge. Option to export to JSON.
edge://predictors — Lists auto-complete and resource prefetch predictors.
edge://prefs-internals — JSON data listing preferences and their status.
edge://print — Print Preview page.
edge://process-internals — Information about site isolation mode and the sites that are isolated.
edge://push-internals — Push Messaging debug snapshot.
edge://quota-internals — Disk quota information including available free disk space for the profile directory.
edge://sandbox — Detailed sandbox status for Edge processes.
edge://serviceworker-internals — Service Worker information.
edge://settings — Opens the main Settings page of the browser.
edge://signin-internals — Details about the sign-in status, refresh tokens, email addresses and more.
edge://site-engagement — Site engagement scores for every visited site.
edge://supervised-user-internals — Removed.
edge://sync-internals — Provides lots of information about synchronization in Edge.
edge://system — System information, e.g. Edge and Windows version, whether enrolled to domain, and more.
edge://terms — License Terms.
edge://tracing — Record, load, and save trace data.
edge://translate-internals — Provides information on the built-in translation functionality.
edge://usb-internals — Option to test USB devices and a devices list.
edge://user-actions — Lists user actions.
edge://version — Edge version information including command line parameters and variations (experiments).
edge://webrtc-internals — create WebRTC dumps.
edge://webrtc-logs — Lists of recently captured WebRTC text and event logs.
Update 21 April 2021
Here’s an interesting WordPress fact. If you enter a http link as edge://<widget>, WordPress strips the “edge:” off, just leaving //<widget>
Further details here.