Start with one beat
In Solfaapp, a complete beat adds up to 1. Four notes at ¼ each fill it exactly; two notes at ½ each do the same. Choose the note length before placing the next note, and the editor shows the space still available.
Use silence deliberately
A rest means silence. It can appear before or after a note and can use any supported length. If a voice starts later than the others, a rest can make that silence explicit.
Carry a note forward
A pull continues a note that already exists. It may fill a full bar when it follows a note from the previous bar. A pull cannot begin without a preceding note in that voice.
Check before export
The editor lets you work on an unfinished idea. During PDF export it points out incomplete bars, so you can fill the missing time or decide how to finish the phrase. Rests and pulls count for their chosen lengths.