Questions

How do I select a non-standard baud rate on a serial port?

How do I use a serial port that was not detected?

When you open a new connection it will make a URI that has all the settings and what comport to use. You can manually edit this URI to use settings and devices that are different that the standard settings.

On Windows the URI uses this format:

COM[Port]:[Bit Rate],[Data Bits],[Parity],[Stop Bits]

On Linux the URI uses this format:

COM://[Device Path],[Bit Rate],[Data Bits],[Parity],[Stop Bits]

You can open a new connection using dialog and select any setting then edit the URI in the main window, or you can just type a URI directly and it will open a connection with thoughs settings.
You can also use File->New Tab From URI... for more info about the available URI's and find examples.