Drain Hole in Transmission Case

that's the weep hole for the bell housing. The next step is trying to figure out if it's engine oil or gear oil.

if engine oil, either the rear main seal is leaking, which would mean pulling the bellhousing, clutch and flywheel to replace, or it's just oil that has managed to get under the flywheel inspection plate after spilling oil from the filter during a change, and it's run down inside the bh to the weep hole.

If it's gear oil, could be the clutch shaft seal or o-rings between the bellhousing and intermediate plate. Bellhousing has to come off for any of those.

It could also be one or more bell housing studs piercing into an oil reservoir of some kind, but usually the oil comes out around the nut/washer when that happens.

If possible, ignore it until you want to replace the clutch.