TT will generate initially one f1116 when it sees foreign tax paid greater than the exemption.  The number of f1116's that are needed is determined by how many distinct foreign countries withheld taxes, not the number of 1099's and each f1116 will accommodate 3 countries.  If there are more than 3 countries, TT will generate additional f1116's as needed during the foreign tax credit interview.

All three 1099-DIVs are RIC or "various". The f1116 is for one broker only and does not include the data from the other two which were issued by a different broker. My 2018 taxes included 3 f1116 forms, one for each 1099-DIV. 

Is there a way to force it to create a f1116 even if not needed? Can I link to an empty f1116 and force it to import the data?

I don't know how to do what you are trying to accomplish.

The correct answer is "don't worry about it" and continue on. Near the end of Deductions and Credits TT notices the orphaned 1099-DIVs and asks some questions, then adds those values to the existing form 1116. Now all 1099-DIVs are accounted for and the error flags has gone away and there is only one form 1116, unlike my 2018 return.

It seems odd to me that part of the work is done after importing the data and part is done much later in the interview. Feedback from the error flags stating that the issue will be resolved in Deductions and Credit section would be very helpful.