Vaadin Flow --lumo css variables not recognized by IDE (Intellij)

As per this question…

My IDE (Intellij Idea) is unable to find the css variables like --lumo-space-s. From what I can tell they get magically added in at runtime. Is there no good way to let your IDE know about all of these variables? Anybody else had this problem?

Got this problem too. Still don’t know what’s going on.
Can anybody provide an answer for this?