Pause extrusion without ruining filament?

Hope this helps:

To keep things simple, i offer a Easy and cheap way. (Works for me)

1. Chop off the uneven bits from both ends, ( 5 seconds)
2. Melt the two ends together using acedone or heat. (up to 40 seconds to cooldown)
The joint doens't have to be perfect because, you will then:

3. Use a Metal file to shave/File off the unevent bulbous round parts where the cable joins together till it's straight again. (20 to 40 seconds), thus making the joint clean and relatively smooth once again.

I have done this in under 1 minute successfully because I use a drill and the sander part from assembling the filastruder... like filing my fingernails... easy. Just try not to strain that part too much.

Do it slowly during your first attempt till you get the hang of it.

the key issue is to file it down to at least (or smaller) than your nozle width. e.g 1.75mm, file to 1.7mm for that part.

If you file it smaller, it won't hurt as such a small section does not significantly affect print as the printer eats though that uneven part in around 3 seconds.. you probably won't notice it at all.
The main danger is that you don't file it down enough and it jams.

I use a melt filter, what i do is cut off the stringy part that doesn't meet desired diameter bring the nozzle to temp and extruder a little bit.  I then turn off the auger and stuff the filament you want to connect to back inwards towards the nozzle slowly.  then turn the auger back and and you should be all set.  If you get good at this you can even do it with barely a transition between the filaments.