Just use P-ify by paphonb, many features of P beta there, its awesome!
1. have the launcher installed (the one you linked)
2. install xposed installer apk from here: https://forum.xda-developers.com/sho....php?t=3034811
3. download xposed framework zip: https://dl-xda.xposed.info/framework/sdk27/arm/
4. reboot to recovery. MAKE A BACKUP of /system or full. In case anything goes wrong/ bootloop
5. install xposed framework zip & reboot
6. open xposed installer -> it will show xposed framework is not active -> reboot again. Open xposed app again, now it will show its active!
7. install p-ify apk https://forum.xda-developers.com/xpo...tures-t3764556
-> you can find latest apk in 2nd post (link to github/releases)
8. activate it in xposed app, then reboot.
open p-ify app to enable/disable features. (when new app switcher is not active)
It looks like much to do, but it takes may 6mins at all, 10 if you count the wait for the backup
Note: some custom roms may have some weird issues. LineageOS 15.1 works perfectly throught!