TextEdit on Mac supports tabbed windows, allowing you to manage multiple documents within a single window. To enable and use tabs in TextEdit:
- Show the Tab Bar:
- Open TextEdit.
- Go to the View menu and select Show Tab Bar.
- Create a New Tab:
- Click the + button in the tab bar to open a new tab.
- Merge Existing Windows into Tabs:
- With multiple TextEdit windows open, go to the Window menu and choose Merge All Windows to combine them into a single window with tabs.
This feature is available in macOS Sierra and later versions.
For a system-wide setting to prefer tabs across all applications that support them:
- Open System Preferences.
- Go to the Dock preferences.
- Find the option Prefer tabs when opening documents and set it to Always.
This adjustment will encourage apps to use tabs instead of separate windows when opening new documents.
Source: https://osxdaily.com/2017/01/24/using-textedit-tabs-on-mac/