Council minutes [Ratsprotokoll] online: Digitized records from Marchivum. Search on Datenbanken. There is usually an index at the end of the pdf file for the years covered. Keep clicking on the last year and it will bring up the next years in that range. They are digitized to the year 1721 [May 2024].
An overview of the above collection that is easier to use can be found at Stadtbuecher.de: https://stadtbuecher.de/de/stadtbuecher/deutschland/baden-wuerttemberg/mannheim/obligationsprotokoll/
See "Das Baugewerbe in Mannheim in Vergangenheit und Gegenwart by Franz Krug on Google books: https://www.google.com/books/edition/Das_Baugewerbe_in_Mannheim_in_Vergangenh/PgBRAQAAMAAJ?hl=en&gbpv=1
'Compendium über alle von anno 1697 bis 1734 ... aufgegebenen Obligationen und Cautionen mit Nennung der Debitoren- und Creditorennamen sowohl als Jahr, Monat, Tag, Pagina auch der Hypotheken- und Unterpfänder und zwar soviel die Debitores betrifft deren Zunamen secundum Alphabetum'
Compendium of all bonds and cautions issued from 1697 to 1734 ... issued bonds and cautions with the names of debtors and creditors as well as the year, month, day, pagina and also the mortgage and sub-pledges and, as far as the debtors are concerned, their surnames secundum Alphabetum'.