Recently I had filement break mid-print. The breakage was just above the hall-effect sensor inside the tool-head, so I could not simply disconnect the bowden tube and pull the filament out. The recommended fixes were to disassemble the extruder and/or the hall-effect sensor to get to the filament.
Daunting enough, but what made this especially difficult was that the printer had locked-out any of the tool-head movement controls, so I could not position the bed and the tool head where it would be easier to do the above surgery.
That’s request number one: do not lock out the controls in this situation.
However, this was just at the start of the print, so I took a different path.
I power-cycled the printer. This cleared the error, but since the short segment of filament was still in the hall-effect sensor, the printer thought that there was simply filament loaded from the external spool. In this state I fed some differently-coloured filament in through the bowden tube, and directed the printer to extrude while pushing lightly on the new filament. The old filement was extuded, and the extruder caught the new filament as expected.
I kept extruding until the new filament was coming out, then I hit “unload” to have the printer cut the filament and I could withdraw the sacrificial filament. Printer fixed; problem solved.
Second request is to make this method available and suggested when there’s a filament breakage mid-print.