Voices issue in bass

I have a bass line entered - I now want to add a tenor part in another voice. The bass line is in “down-stem Voice 1”. I can’t figure out how to get a voice that I can enter the tenor into. If I press Shift-V then the first note of the bass changes to “up stem Voice 3” Previously it changed to “up stem voice 2”. But I don’t want to change the voice of the bass, I just want to enter a new voice.

Pressing Shift-V outside of note input, with notes selected, changes the voice of the selected notes. Each time you’ve pressed Shift-V with a bass note selected, you’ve created a new voice on that staff.

To input notes into a specific voice on a staff: start note input, then use either V to cycle through already-active voices on the staff, and then input notes into the voice indicated by the caret; or use Shift-V to create a new voice into which you can then input notes.