Windscreen washer fluid level

Yes, it would have been more logical to combine the two reservoirs into one: as we generally use the rear window washer much less often than the front one, its reservoir is usually still nearly full when that of the windshield is already empty. You can improve the situation by connecting the two reservoirs together. Drill a hole into the sidewall of the reservoirs near the bottom. Fit a banana jack into this hole (don't forget to use some sealing gasket or silicone sealant before you secure it with a nut).