Here is an excerpt from the Notion User Guide, which can be found on page 9.11
There may be expressions or articulations defined in your VSTi, that do not
exist in Notion. To add these to your score, follow the steps:
1. Create the expression name in the Preset.xml within the Preset folder
2. Create a Rule for playback for this expression, within the Rules Editor in
3. These custom expressions can now be recalled from the palette - click
the arrow, place on the score, and then select which custom expression
you want to add.