It is possible to perform a second jump mid-air by letting your shield get hit by a Remote Bomb explosion.
To perform this technique, first place a Remote Bomb on the ground. With your shield equipped, detonate the bomb with L and at the same time perform a backflip/sidehop/fronthop. If timed correctly, you should be able to do a second jump mid-air, from which you can then Shield Jump to gain even more height.
The most optimal combination for height is first a backflip and then a fronthop - but two fronthops may be more beneficial in some scenarios to gain slight distance. It is important to note that this trick may not be performed liberally, as it requires a very powerful shield. The overwhelming majority of shields available cannot withstand even a single attempt before breaking - the Hylian Shield, Daybreaker, and Ancient Shield being the only exceptions.