There is a workaround using AutoHotkey.
The following code allows Win + Tab
to simulate a right mouse click. After that, you can move your finger on the touchpad to pan the graph in the Blueprint editor.
And you can custom the key in the autohotkey
#IfWinActive ahk_class UnrealWindow
#Tab::
Send {RButton Down}
KeyWait, LWin
KeyWait, Tab
Send {RButton Up}
return
#IfWinActive