Hydraulic clutch pedal question

In most OEM assemblies, A hydraulic clutch/slave setup is not adjustable. It sort of self adjusts as the clutch wears ( really just the release point moving farther away ). After a certain point you can't get reverse ( or first gear depending on what gear box ) without some grinding. Nature of the beast as it were. I dont know why or how aftermarket would be any different.
Then again... The hex shaped section shown in your pic is/works as a turnbuckle. Maybe adjust the master stroke there? That would adjust the slave stroke also but... It can only travel the full length of its stroke.
It's much more likely that turnbuckle only adjusts the pedal height. Bottom line, If this was a factory build, the factory service tech would say, "you need a clutch".