In previous ONI updates, the priority tool worked better.
When using the tool, clicking on a tile makes everything in that tile the chosen priority. That is still the case.
However, when looking at just ventilation, or just plumbing, automation, etc, when using the priority tool it used to affect only the displayed system. i.e. when looking at plumbing systems, the priority tool would only change the priority on pipes or plumbing related items. Now it changes the entire tile.
IMO, it was a much more versatile tool in the past and the loss of functionality is crippling.
use a system filter and use the priority tool on a tile with multiple items needing a priority.