You can create a post function to calculate Issue Score value on any Issue during a transition. Provide a JQL here about where you want to calculate the Score value. If empty, it will be only applied where the transition is executed.
To add a post function to a transition, edit the workflow that contains the transition, select the transition, then click Post functions in the properties panel for the transition.
To add a post function to a transition:
In diagram mode, select the transition arrow. In text mode, select the transition's name from the Transitions (id) column.
The Issue Score post function will be displayed with the configured JQL in the list of post functions. Options for editing or deleting a post function, and for changing the execution order, are at the right of the tab (hover there to see them).