"Very technical but very useful"
look at small movement of the right hand. The left one is damping all movement and tension in the string. Don't focus on it.
Simple end : just un-make the round of string around the diabolo.
with this profile view, you can see that the right hand is a little bit behind the left one.
You have to surround the diabolo with the string with a movement of the right hand then to draw from a rather violent blow with the right hand to the top on the right but with the slightly flexible wrist: No the dry blow! The left hand is fixed slightly above the shoulder and on the left and the flexible wrist which tightens the string in order to tend it but not too much. The string must thus remained slightly tended but it must also keep an orientation slightly oblique compared to the diabolo (normally the string remains perpendicular to the axis of the diabolo. Here the left hand remains slightly ahead compared to the right hand) so that the string does not overlap on the ring of the diabolo. In short once in top on the right it is still necessary to gently draw this time with the right hand to the bottom on the left. The diabolo must remain on a diagonal that looks like that: "/", close enough to the right stick. Don't forget that this is an acceleration ... The left hand must nevertheless rewind the string between each traction of the right hand and an unperceivable way (both for the public the juggler himself ....).
A piece of Advice: You can train to make the "round" acceleration who approaches "Chinese" acceleration: You make a round of string around the diabolo, one forces the diabolo to roll from the right-hand side to the left and when it is on the left you make as if it were launched but there remains rolled up by the string. Then one draws with the left hand to the bottom what brings the diabolo to the right-hand side. and so on...
History of diabolo
You are at the first trick