DSSI plugins don't obey volume or effects

With dssi instruments, volume automation works, but volumes in the pattern doesn’t.

In the volume column or volume commands in the pattern effect columns?

um, both =) …but i was referring to values in the volume column.

the volume column sends velocity data to plugins, i think,
so you would have to set velocity to modulate volume in the plugin interface

sample effects are only for samples, but you can use an instr. automation device to control parameters in the plugin like you would use sample effects
you could also use this for your volume settings if your plugins lack velocity>volume

HiddenCinamon made one part of his point.
In the effect column you can also use track/channel-volume commands (similar to what you automate), these should work.