I often switch between my laptop display and a connected larger screen. I also sometimes need to show some emails with screen-share in like Google Meet etc. In some of these situation I need to quickly enlarge the font size of the email text. I sometimes automatically go for Ctrl+Mouse Wheel or Ctrl+KP_Add to find out it doesn’t work.
Allow using the “Scaling” option under the “Appearance setting” using keyboard shortcuts (default should be Ctrl+KP_Add and Ctrl+KP_Subtract (Numpad + and -)). Also holding Ctrl and scrolling Up, Down on Mouse Wheel or touchpad should change the scaling.
This is the alternative solution originally I wanted an Inbox Zoom that would be decoupled from UI Scale but meh.
VS Code is also an Electron app and it supports this feature via Ctrl+KP_Add and Ctrl+KP_Subtract. I only use web apps as my other mail clients (Outlook, Gmail) and this is covered by the browser, I think all browsers support this.