Odoo Enterprise does not offer a built-in toggle for this since When performing manual or batch reconciliation directly from the journal items list (Accounting > Journal Items), the system allows selecting and reconciling multiple entries even if they belong to different partners. It does not enforce partner grouping in this context, providing flexibility for manual adjustments, though this can sometimes lead to unintended matches if not handled carefully., but there are two practical solutions:

Option A: Use the OCA module account_reconcile_restrict_partner_mismatch

This module from the Odoo Community Association (OCA) prevents reconciliation between journal items with different partners. It enforces that both entries must have the same partner, or One entry must be empty (no partner), and the other must also be empty.

Option B: Reconcile from the Partner Ledger or Payment Matching screen

These views automatically group entries by partner, reducing the risk of cross-partner reconciliation. Recommended for most operational workflows (e.g., customer payments, vendor bills). also you can use the Auto Reconcile feature (Accounting > Accounting > Reconcile > Auto Reconcile), which opens a wizard where you can select specific partners, accounts, and date ranges. This processes reconciliations per selected partner, naturally limiting to one at a time.