Hi @dnaki,
generally, the latest released KNIME version is always the ‘releases’ branch with the latest date, i.e. ‘releases/2019-12’ in this case. However, the dialog window you showed is only about which branches should be initially cloned when importing the knime-sdk-setup repository, which means that you can easily get the latest release branch afterwards no matter what you select in this dialog window. This can be done switching to the latest releases branch after the repository has been cloned. Here, you can just leave the selection as is in the screenshot.
Cheers,
David