What is ⌘ Cmd + U keyboard shortcut for?

Apple macOS - Underline the selected text, or turn underlining on or off  

Apple iBooks - Apply underline to selected text  

Roll20 - Add selected object(s) to turn tracker  

Firefox (macOS) - Page Source  

Notability - Underline  

Roam Research - Search the database (moves cursor to search bar)  

Bear (macOS) - Underline  

Tomboy 0.23 - Underline  

Google Docs (macOS) - Underline  

Typora 0.9.81 (macOS) - Underline  

Xcode - Underline the selected text or turn underlining on or off (equivalent to the Underline command)  

Adobe Premiere Pro (Mac) - Make Subclip...  

Adobe Premiere Pro (Mac) - Underline  

Adobe Illustrator (Mac) - Show/ hide smart guides  

Aseprite 1.2.27 (macOS) - Hue / Saturation  

Corel Painter (Mac) - Ungroup  

Corel Painter (Mac) - Ungroup  

Autodesk Mudbox 2022 (macOS) - Show Selected  

Framer X - Underline  

Harmony 20 (macOS) - Preferences  

Visual Studio Code (Mac) - Undo last cursor operation  

Arduino IDE - Upload sketch  

CodeMirror - Undo the last change to the selection, or if there are no selection-only changes at the top of the history, undo the last change  

Team Explorer and Azure DevOps - Underline  

Sequel Pro 1.1.2 - User Accounts…  

Looker 6.8 (Mac) - Share  

Looker 6.8 (Mac) - Share  

Reserved Mac - Underline the selected text or turn underlining on or off.  

Atom (macOS) - Undo selection  

Mode SQL Editor (Mac) - Underline  

iTunes 11 for Mac - Stream audio file at a specific URL to iTunes  

Cisco Jabber (Mac) - Underlined  

Discord (macOS) - Toggle channel member list  

Gather Town - Toggle quiet mode (events Spaces) or do not disturb mode (remote work Spaces)  

Adobe Connect (macOS) - Underline text  

Blackboard Collaborate (macOS) - Ungroup selected objects  

Zoom (iOS) - Display/Hide manage participants  

Twitterrific 6 - Show selected item's author profile  

Zoom (Mac) - Display/hide Participants panel  

Signal (macOS) - Attach file  

Luna (DAW) - Quantize Selection  

Luna (DAW) - Quantize  

Quip - Underline the selected text  

Google Sheets (Mac) - Underline  

Logic Pro 10.6 - Set locators by regions/events/marquee and enable cycle  

coda.io (Windows, Mac) - Underline  

SmartDraw - Underline Text  

Google Sheets (iPhone & iPad) - Underline  

Miro (macOS) - Underline  

Guitar Pro 8 (macOS) - Brush up  

Google Looker (macOS, 2023) - Share  

Google Looker (macOS, 2023) - Share  

Vectorworks 2020 (macOS) - Ungroup  

iPad Magic Keyboard - Underline