There are different ways to accomplish your goal, depending on your specific needs.
Viewport Render
The viewport can be rendered through View > Viewport Render Image.

Screenshot of the active area
A screenshot of the active area can be created using the following steps:
- Hide the gizmos

- Open the operator search F3 and search for Save Screenshot.
- Run the Save Screenshot operator (
bpy.ops.screen.screenshot()
).
- Uncheck the Full Screen property (this will only include the active area) and save the image.

Fullscreen mode & third-party software
The following steps enabled the fullscreen mode and allow you to take a screenshot with a third-party tool:
- Hide the gizmos

- Switch to fullscreen mode through View > Area > Toggles Fullscreen Area (Ctrl+Alt+Space).
- Use a third-party tool to create the screenshot
- In order to leave the fullscreen mode move the mouse cursor to the upper right corner and click on the icon
. Alternatively you can also press the shortcut again Ctrl+Alt+Space