To get 4/4 in a song that starts as 3/4, you must select a style for the song that is in 4/4. In other words, you can always change to fewer beats (and change back), but not more beats than the original style.

A small wrinkle: since you want the 3/4 to start at the beginning of the song, you will get a warning if you use F5 on the first measure that says the style change at bar 1 will change the overall song style. One workaround is to use an empty measure at bar 1 (like C.), make the style change in bar 2, change to 3 beats per bar, and then go back to the chordsheet to change the Bar for beginning of Chorus number from 1 to 2.

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