Unfortunately, there is no way to influence the left-to-right ordering of nodes in a top-to-bottom or bottom-to-top hierarchical layout when importing a graph from Excel.
The only workaround available is using a two-pass approach (which does need some manual repositioning of nodes in step 2):
Import your data from Excel with "Layout" set to "Hierarchical" on tab presentation.
Right after importing, reorder the nodes manually. You need to make sure the nodes do not overlap, but otherwise it suffices to place them at roughly the desired location (no need for pixel-perfect placement).
Run the Hierarchic Layout once more but with option "Use Drawing As Sketch" on tab "General" enabled. (Note, you may not have this option enabled when initially importing data from Excel.)