If you'd like to disable a vendor, whether temporary or permanently, from things like receiving purchase orders, updating inventory, shipments, etc. there are a few things you can do essentially 'turn off' these features.
Option 1: Managed in Duoplane
Duoplane has a vendor-level option in every vendor's wholesale settings labeled "Managed in Duoplane". By default this option is toggled to "YES", however if you toggle it to "NO" what this does is hide POs assigned to this vendor and not send the POs to them.
This option is useful in cases where items are fulfilled outside of Duoplane. Maybe they are giftcards that are automatically fulfilled, or something that is fulfilled in-house manually outside of the Duoplane workflow. The association of that line item on the order will still be made with the vendor, but Duoplane will not take any action beyond that.
Option 2: Accepting new POs
If you would like purchase orders to not be assigned to the vendor at all (as if the vendor didn't exist or didn't have an association with the line items on the order), there is a vendor-level setting in every vendor's wholesale settings labeled "is accepting POs" which can be toggled to "YES" or "NO".
By default this option is set to "YES", but if toggled to "NO" the vendor will not be assigned POs. Note this may result in some new orders being flagged as needing a vendor, since if there is no alternate, Duoplane will not have anyone to assign the items to for a purchase order.