I think -- and you should test yourself -- that when the Action pane is active it becomes window 1 and the Editor becomes window 2. That's why the path changes.
In which case:
tell application "System Events"
tell process "Keyboard Maestro"
if name of window 1 is "New Action" then
set winIndex to 2
else
set winIndex to 1
end if
tell window winIndex
tell group 6
tell splitter group 1
tell scroll area 3
tell scroll bar 1
set value to 0 -- moves thumb to top
-- set value to 1 --moves thumb to bottom
end tell
end tell
end tell
end tell
end tell
end tell
end tell