Dunno where to ask, but what is this button, what does it do? Had the same button on my other manual transmission car. Citroen C5 MK1 (2004) : r/AskMechanics
Car Gear Shift Knob 5 Speed Manual for Citroen C5 01 08 Xsara Picasso 99 08 Car Accessories|Gear Shift Knob| - AliExpress