How do I set off loans between our companies without moving cash?

Intercompany Reconciliation → Offsets. Pick the balance date, the journal date and whether the journals post or stay draft. Offsets lists the loans that can be set off — two companies owing each other, or a loop of three. For those you tick it prepares one board resolution and one manual journal per company, with the chairman and signatories from Company Structure. Post files the resolutions and posts the journals together; the figures are recomputed from the balances at that moment and the post is refused if they moved since the screen was drawn.