use jdk15 for idea runtime jdk, but idea lost markdown preview, anyone can help me ?

hello, i am linux user. i want to use zgc, so i upgraded idea jdk version to jdk15, which version is 15+36-1562.

currently i got one problem, i can not use markdown preview.

in Settings->Language & Frameworks ->Markdown, i saw tips "There are no available preview providers"

i try add vmoptions set javafx path but it does not work. options bbelow:

--module-path /xxxx/javafx-sdk-18.0.1/lib
--add-modules javafx.controls,javafx.fxml

i used default runtime jdk, markdown preview was worked, but jdk15 can not.