Can't enable language injections
I have a custom language injection, but I can't check mark any of them in the settings--they are grayed out. I am using Community edition. Note that a plug-in I use called TeXiFy-IDEA created the luacode injections, and they do work (despite not being checked off in the settings).

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Kale sorry for dragging with the response. I reproduced the issue with other custom injection types and filed a usablity problem to our tracker, feel free to upvote IJPL-197508 and follow it for updates.
In my tests the injection checkbox became responsive only after I selected class methods in the Language injection settings. It might be that in your case some required configuration parameter (presumably Places pattern) was not filled. Hope this information will be helpful.