By default, dynamics and slurs are automatically linked when you copy them to other staves at the same rhythmic position. You can disable this behavior so dynamics and slurs are not linked by default.
Procedure
- Press Ctrl/Cmd-, to open Preferences.
- In the category list, click Note Input and Editing.
- In the Editing section, deactivate Link dynamics and slurs to existing items when pasting.
- Click Apply, then Close.