what is this cable and where can I measure the gear oil level?

hi, again 2.0i saab 900II (my1997) switchcar xD found a loose cable next to the safety box when looking in the engine room and doesn’t know where it belongs…maybe one of you? it has a green border and is relatively short, so I couldn’t pull it any further than it can be seen. and I lose minimally driven oil through the leaky shaft seal ring on the gear box and would like to know how to change the a) and b) how to get the gear oil out. my manual only gives me the statement that you should measure/check the one at the inspection, but not where. and how/where do I fill it up? mfg