So have messed about with the fluid system 95 times and still not fixed it, what's left?
The extended slave rod dodge has been around for years as has two pistons in one slave, but neither lasts for ever and clutch drag returns.
Several people have already mentioned checking the crank end float by pushing and pulling on the crank pulley, it was always a good reason not to buy a Beetle in particular. Did you? The crank runs away from the slave and you get partial clutch operation. BTW I have no idea why this works, but it does.
The next is did you waggle the gearbox input shaft? If the shaft bearings are worn the weight of the driven plate can make it drop enough to give you limited power transfer from the top and bottom edges of the plate. It behaves like it's turned into an auto box and creeps in 1st gear.
Driving it like this puts all the grief into the syncro cones, which then have a short life.