Engraving lost when exporting flow

When importing a flow from another project with the same instrumentation, all my barlines are reset to individual staves. Shouldn´t sections be transferred with connected barlines when opting for “merge with existing players” ?

If you import a flow into a project, then the ‘receiving’ project’s Options – Engraving, Notation, Layout, etc – are maintained. You’ll need to change the Notation Options > Barlines settings, which I think will be set to your defaults.

I suppose there’s an argument that because Notation Options are per flow, that they should be held within an exported/imported flow; but there may be reasons why that’s not the case.

Thanks, yes that makes sense.
However, I can´t see how I change the notation options any further. I have the “Draw barlines in staff” selected, but Dorico never joins any barline when adding a multiple-staff instrument or section…

Hard to say what’s going on without seeing the project: but you can always use the Library Manager to compare the original document that the Flow was in with the new one.