For me assembly of the Bowden adapter is easy, but to take it apart has meant that the plastic parts including the PTFE gets too damaged to use again.
I first tried making a tool to remove the black clip, but this was not strong enough (ABS). Then considered making the black clip longer, but thought it would still probably break.
Then i considered making a slotted coupling so that i could twist to release it. But unfortunately i do not have the facilities to make it.
Last of all decided to thread the adapter using a M14x1 tap (for the 3mm adapter). With a silicon ring to hold the tube. 3mm thick.
The 1.75mm adapter would use a M10 x 1.5mm tap. A M10 x 16mm mild steel bolt with the centre drilled, also some 2mm silicon or maybe flexible filament to use as the seal.
The adapters have a 13mm opening (3mm), and 8mm for 1.75. The outside diameter is 16mm, so that is why i selected a fine thread for the 3mm adapter.
Included are all the items described. The twist connector may be useful to people with a CNC machine.