For example, you could enter ñ by holding Alt and typing Numpad1 Numpad6 Numpad4, then releasing the Alt key.
To this day, this remains the best way to insert the character, I have tried the PowerToys Quick Accent [1] but I had so many missed characters when typing fast.
[1] https://learn.microsoft.com/en-us/windows/powertoys/quick-ac...