Let me get a clear picture on the question(s)
1) "...with internal part numbers." - Do you need internal part numbers? I would say you only need then when you do your own production.
2) "Each part number .... corresponds to multiple manufacturer part numbers, suppliers" - then why not almost like the BoM's I have seen of 20 years ago: "Resistor, 10k". It did not even have a size or tolerance mentioned.
3) "How can I import the data of multiple manufacturers into a single component into the database library? Knowing that I will be importing the parameters from the manufacturer parts search panel." - So data specific for a single MPN should be imported in a database that should handle multiple MPN. And Altium should understand it all?
These question may sound negative, but I want you (and others) to think also on the reasons "WHY".
If the component is not critical, you could go for the generic: "Resistor, 10k, 1% 0603".
However, when it becomes more critical, I would opt for a single MPN for a single component.
I posted a comment here before on (schematic) library data
https://designhelp.fedevel.com/forum...9667#post19667 As you can see, there is too much that is MPN (Manufacturer Part Number) specific to store in a database you describe IMHO.