I understand your frustration and (to some extent) share it. But the problem has nothing to do with how SmartSuite handles its (hidden) primary keys. It's how it handles the primary field for a table — what SmartSuite by default calls the record's \"Title\".

In Airtable, the primary field (there called by default \"Name\"), is very like SmartSuite's primary field, a stand-in for the hidden primary key. Airtable's approach is, in my opinion, worse in one respect and better in another.

Airtable permits putting exactly the same value into every record of this primary field. It says in its docs that you shouldn't do it, but it's possible. SmartSuite tries harder to emphasize that the record title should provide an unambiguous identifier for the record. +1 to SmartSuite.
On the other hand, Airtable allows the primary field to be many different data types, including a proper formula field. Experienced Airtable users make their primary tables formula fields quite frequently, so that we can do things like combine customer name, order date and order # in a single field. In SmartSuite, your options are much more limited. If you pick the Autogenerated option, you aren't really allowed to enter a formula. You can't for example use the CONCAT() function there. All you can do is enter field references or simple, literal text strings.

Now, to answer your question.... You may enter something like this into the Autogenerated 'formula' field:

[ProductName]          [Customer]

where there are 10 spaces between the two field references. But apparently SmartSuite treats those spaces the way that spaces are typically treated when rendering HTML: duplicates are automatically removed. NOTE: I do not know that that is what's happening. It's just what it looks like to me.

I'm not sure why you need such big space. I sometimes use a pipe character as a separator in my primary field formulas in Airtable and SmartSuite, e.g.

[ProductName] | [Customer]

And that seems to work pretty well. But you could also insert characters, anything other than an empty space. So this should work:

[ProductName]⸳⸳⸳⸳⸳⸳⸳⸳⸳⸳[Customer]

There I've inserted 10 raised dots between the field references. Hyphens would work, too. Or underscores.

How to have a double space between two fields in the auto-generated primary key?