Multiple HALion Sonic SE Windows Opening On Launch

Two or more instances of the same. Any reason why? Seems to be making load times way slower.

Depends on the size of your project. IIRC each instance of HALion can handle 16 instruments. If you’ve got more than 16 instruments in a project, Dorico loads multiple HALion instances.

There’s also a preference in the Play section to not show the plugin windows.