Answer: Introduced in v5.1.16

If tiddler has both: this AND tag that create an orange border.

[data-tags*="bar"][data-tags*="froz"] {
  border: 2px solid orange;
}

If your CSS looks like this:

[data-tags~="this"] {
  border: 2px solid blue;
}

[data-tags~="that"] {
  border: 2px solid red;
}

this creates a blue border that creates a red border If you swap positions, you get it the other way around.

Learn more about possible attributes!