To clarify upon what "harrymc" said:
In remapping keys using this method be sure to Click on "Remap a shortcut" not Remap a key" If you try to do "remap a key" then it will only let you choose "Alt" OR "Tab" but not both.
Alternatively, if remapping keys with powertoys isnt for you then I recommend using fancy zones to do exactly what harrymc said, and then you can remap keys using AHK (v1 or v2).
In V2 writing a simpleAHK script to change your hotkey would look like this:
Requires AutoHotkey v2
SingleInstance Force
InstallKeyboardHook()
Persistent()
!Tab::#PgDn
Now, I will say, implementing the fancy zones suggestions from HarryMC is a bit trickier and I myself am having some issues getting that working. Harry, if you would please post a more specific guide (maybe with some screenshots) it would be much appreciated.