MuseScore is an open source and free music notation software. For support, contribution, bug reports, visit MuseScore.org. Fork and make pull requests!
A dynamic assigned to specifically voice 1 (only) should go below or above the stave, according to whether it is the only voice present on the stave at that point. This is analogous to how stems all go up and articulations go above when a downstemmed voice is present, but they don't need to when only voice 1 is present. (And assuming that 'Position' is set to 'Based on voice'.)
Adding a dynamic from the palette with the 'Ctrl' pressed should assign the dynamic(s) directly to the voice(s) of the currently selected note(s), if any, rather than to 'All voices'.
A dynamic assigned to specifically voice 1 (only) should go below or above the stave, according to whether it is the only voice present on the stave at that point. This is analogous to how stems all go up and articulations go above when a downstemmed voice is present, but they don't need to when only voice 1 is present. (And assuming that 'Position' is set to 'Based on voice'.)
Adding a dynamic from the palette with the 'Ctrl' pressed should assign the dynamic(s) directly to the voice(s) of the currently selected note(s), if any, rather than to 'All voices'.