"disable touchpad while typing" is missing

There is no longer an option for "disable touchpad while typing" in xfce's Settings Manager -> Mouse and Touchpad.

To be clear: this is a new issue. Yesterday, everything was working fine on my laptop. This morning, my horror was realized when I couldn't type anything without my thumbs constantly tapping the touchpad, causing every other word I typed to delete the previous paragraph. I went to the xfce Settings Manager for Mouse and Touchpad, and I found that the "disable touchpad while typing" option was totally missing.

I'm assuming that this was caused by a recent update? Here's my system info:

OS: QubesOS 4.0 Xfce: 4.12 Laptop: Asus UX331U

When I'm in the "Mouse and Touchpad" window, it lists my touchpad "Device" as "ELAN1200:00 04F3:309C Touchpad".

Please let me know if there's any more info I can provide to resolve this issue.