There does not appear to be a keyboard equivalent for moving around the different options on a window other than up and down in a selection list.
I have reviewed the key binding UI and can’t find a keyboard equivalent that allows you to move around to the different areas of a Zynthian screen, other than scrolling up and down in a list by using the up and down arrows. The right and left arrows typically move you to other screens, such as other MIDI channels, rather than allowing you to select the controls shown for a particular instrument on a particular channel.
You have full control of Zynthian from a computer keyboard (or MIDI or OSC). Keys are mapped to the 4 encoders and switches of the V4 which gives full V4 control. Keys can also be mapped for any switch or encoder on the V5.
To simulate turning the knob using the keyboard, it is necessary to emulate clockwise (value 1) and counter-clockwise (value -1) rotation. The knobs are numbered from upper left (0), lower left (1), upper right (2), lower right (3). A finaly the name of command is Zynpot. By default it is set as follows: