Well not exactly but Sage does have a very nice way to do this in their data tables. Then you need to do some Customization to actually take advantage of this with the UI. We have this built into eBusiness Suite for Sage ERP MAS 500 natively. You might be able to do something with a Custom lookup or just a generic customizer button the main page of Order Entry just not at the line level.

Now back to the data structure to allow you to Manage what you are trying to accomplish. I posted this on the Sage MAS 500 LinkedIn group page as well.

Add the abiltity to create User-Defined Item Aliases. This allows you to create Alias Category then create Item Aliases under the various Categories.

a. How is this accomplished?
The timItemAliasCat table contains a field called AliasType. This contains 2 predefined types that Sage ERP MAS 500 uses today. They are 1 for Customer and 2 for Vendor. So that Items attached to these Alias Types would be maintained in Maintain Customer Items to cross-reference your items to a Customer Item and Maintain Vendor Items to cross-reference your items to a Vendor Item. The cross reference items are then maintained in the timCustItemAliasCat and timVendItemAliasCat tables respectively.

If you look in the Schema Browser at this table and field it shows that an acceptable value in timItemAliasCat.AliasType is 0 as well. So you can create multiple records in this table with ItemAliasCatID of AliasType 0. Then the ItemAliasID (user-defined cross-reference Item would be maintained in the timItemAlias table. You relate each entry in this table to an ItemKey (your item numbers) and an ItemAliasCatKey (user-defined Alias Category).

b. How could this be used?
You can create a category called "Mfg. SKU" and put in the original Manufacturer SKU, not just your Vendor SKU. You can create a category called "Competitor SKU" or "Prior SKU" and let your imagination run wild.

We have done this for a couple of clients and we have added this as native functionality within the eBusiness Suite for Sage ERP MAS 500.

In Maintain Vendor Items scree, we can see only finished goods can be consider , why we are not able to configure Misc Items for vendor

I have no idea which version you are using so this is the next version that is currently being worked on, but this application probably hasn't changed in years.  Here, I can assign a vendor item name to a misc item.