Just double-checking that I'm not missing something on the spreadsheet. From what I can see, there is no way to have a trade pair of systems where one system is one Sector and the other system is in a different Sector (to be clear I *am* referring to Sectors and not Subsectors.) For example, since I'm working on the Hinterworlds Sector and specifically the Hashi Subsector, that Subsector is in the bottom left corner it means that it borders three other Sectors (e.g. Old Expanses, Alpha Crucis, Spica.) So, it seems logical that there will be trade across those Sector boundaries.
On the spreadsheet on the 'Planets Tab' in C2 you choose your Sector, but only once. I'm assuming this is because the sheet wasn't originally designed with multiple Sectors in mind. What would be involved to provide this functionality?