Pad a list with NULLs

In trying to build a list with planar geometry grouped by its x location; such that geometry at the 12th station appears at the 12th index in the list, I am boxed into another corner I cant get out of.

If there is less goemetry than stations, the list needs be padded with nulls before and/or between and/or after the geometry.

If i start with a list of NULLS and use REPLACE, i get NULLs in the branches with the geometry.

If just create a list with the correct indexs for the geometry, it seems I cant add NULLs at the other stations (one per station) as placeholders if you like

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ReconstructListStructure 13.gh (20.3 KB)

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