Newer versions of mainline udev, as included in systemd v235+, support escaped double quotes \" inside the double quotes of a udev rule's value. This is mainly useful for RUN{program}. In simple cases this escaping mechanism can be made unnecessary by replacing the escaped double quotes with a single quote as documented in udev(7) (as in ValveSoftware/steam-devices#11), but in more elaborate udev rules that isn't necessarily straightforward. The merge request that added this is systemd/systemd#6890.

eudev doesn't appear to support this; in ValveSoftware/steam-devices#10, @xrogaan reports that this makes certain rules fail to parse on a system that uses eudev 3.2.7. I haven't confirmed whether the same is true in 3.2.9 (I don't use eudev myself) but none of the commits since 3.2.7 look like they would change this behaviour.

Handling escaped double quotes in the same way as the udev included with systemd would improve eudev's compatibility with third-party udev rules installed to /lib/udev/rules.d by other packages.