In the ledger allocation rule, the "Destination" form does not allow to keep the financial dimension (those not allocated) according to the original value.

If you want to allocate dimension 1, you need to even though define each value of dimension 2 for destination posting. This is not manageable.

Just use the logic of

Main accounts > Legal entity overrides > Allocation terms > Destination ledger account.

This is exactly what is missing in the allocation rule definition.

It would be perfect if this logic could be made available in the ledger allocation rule definition, Destination, too. As is the Main accounts table, the selection should be per single financial dimension (could also be applied in the form "Offset").