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As explained above: Remove all instances of USBPorts Reinstate USBInjectAll (and rebuild your cache if you're caching it but I suspect you're injecting it instead) Reboot Run Hackintool app and, in the USB tab, regenerate SSDT-UIAC table + USBPorts kext Retain SSDT-UIAC table with USBInjectAll kext or use (i.e. inject or cache) only USBPorts kext TrackPad PrefPane should then be back.

Which High Sierra build are you running? And what about kexts you could be injecting from Clover? I assume you're doing that, aren't you? If so, no need to cache the kext from /L/E. This being said, I was just offered to install High Sierra Security Update 2019-005 on the E6220, which I did (build 17G8037)... and TrackPad PrefPane subsequently disappeared (familiar message "no TrackPad detected" reported in PrefPane)! I've identified that the problem was due to USBPorts kext. After reinstating USBInjectAll and re-generating SSDT-UIAC table + USBPorts kext, the TrackPad PrefPane is back with SSDT-UIAC + USBInjectAll or USBPorts only.

Check that you've not installed any other PS2 kext anywhere that would interfere with DrHurt's VoodooPS2Controller R6 (which is the correct kext to use on all E6x30). The kext worked perfectly on my E6220/E6230/E6440 under High Sierra and continues to do so on my E6230 under Mojave and Catalina. And I have the TouchPad PrefPane present too. E6220 under High Sierra 10.13.6: E6230 under Mojave 10.14.6 and Catalina GM (no longer runs HiSie): Various gestures work properly, can't say they all do, especially as I have 2 left hands and big heavy fingers, but many do (show desktop, LaunchPad, Swipe between pages, ...).

If HDEF (or whatever other audio device name) is not defined by default in your DSDT, maybe it is in an SSDT. You can dump all raw BIOS tables by pressing F4 at Clover main menu and then check things out. All extracted tables will be saved in EFI/CLOVER/ACPI/origin folder. But you probably already know that...