Linnebach, vol. 1, pp. 21 and 40 (link at the bottom of this message), explains in the notes that the Titular-Capitaine didn't have a company. So he seems to be the equivalent to the Prussian Stabs-Capitaine.

In a list of ranks in the KGL of 1804, surely reflecting the rank system in the former Hanoverian army, there are:

Wirklicher Capitän
Titulär-Capitän
Premier-Lieutenant
Second-Lieutenant or Fähndrich

https://books.google.de/books?id=e1cMAAAAYAAJ&pg=PA372&dq="titular+capitän"