8 axis install

Yes.

More info, what GUI, how are the axis set up, upload hal and ini files here.

Axis:
XYZ = linear
ABC = rotational
UVW = linear
Not a rule, they can be changed to whatever is needed, but makes it easier to keep track
Simplest way i can think of is to do a config for 4 axis and 4 tandem axis, then edit the ini file to to rename the tandem axis, those will be named X2,Y2,Z2,A2 by PncConf.
Be aware that if using limit switches, the HOME_SEQUECE will be negative for all joints and that will prevent homing, so make the positive and number them as they should be homed.
The hal file has to be edited also as this will result in two joints for each axis, so 4 of them have to be added their own axis "tittle".
Or give the new tool by BigJT a try, see if it does what you need and report back as he is actively developing it:
forum.linuxcnc.org/27-driver-boards/4599...ration-tool-features

Maybe a hybrid approach. Make a reference config with PnCconf and compare the two files (and merge by hand)

HAL / INI are intended to be human-editable. In fact if you go back far enough that was the only option.

Keyboard?
Arrows for joint 0 and 1, pgup/pgdown for joint 2, square brackets on US keyboards for joint 3.
Do not know the rest, yet.
In Axis Gui, there should be letters that ca be chosen fir each axis or joint, then the + and - under those letters will jog the selected axis or joint.