Note spacing in measure-less text

You have system breaks at the end of the measures, the arrows. If you put more measures on a system the notes would move closer together. There are other things you can do to put more notes in a measure.

If you right click the staff, choose Staff/part properties, click the Advanced Staff properties and check Stemless, all notes will be stemless in that staff. This will allow you to put which ever notes you want into the score and they will be stemless. You can slow the tempo down if the notes are too short in time. You can also add notes either by inserting individual notes into a measure or using insert mode for note input. See https://musescore.org/en/handbook/note-input#insert-notes and https://musescore.org/en/handbook/note-input-modes#timewise.

There are other possibilities but these are rather simple and can allow you to do what you want.