I had this same question, but I wanted to search the forums before asking, and I found this post.
Here is the thing... PLEASE consider making an action for "Is key down."
Yes, I see I can make a work around with bools, constantly checking. HOWEVER, I'm on day 3 on a complicated (at least complicated for me) character controller. There are lots of moving parts, and this lack of function is making things much more complex, and difficult to troubleshoot... in fact I'm still not done... although I'm sure I'll get it eventually.
On searching the forum posts, I see through the years, many people asking for this basic function... and the workaround always comes up... and that is fine for a simple FSM... but as things get more and more complex, the lack of this feature makes it more and more difficult to create and then debug.
Thank you for considering!!