Sounds like maybe you are using the default empty score that is provided for just messing around, but when creating new scores, you really should be creating yourself with File / New, and then you can specify the length in the wizard there, along with instrumentation and other details.
But as mentioned, Ctrl+Delete removes selected bars regardless of what score you are starting from.
Comments
Just remove them, see https://musescore.org/en/handbook/3/measure-operations#delete
Or create the score with just 2 measures from the start
Sounds like maybe you are using the default empty score that is provided for just messing around, but when creating new scores, you really should be creating yourself with File / New, and then you can specify the length in the wizard there, along with instrumentation and other details.
But as mentioned, Ctrl+Delete removes selected bars regardless of what score you are starting from.