Dash Jumps: If you jump during a dash without holding left or right, for a few frames you will move in that direction in air faster than you would if you were holding that direction. Doing this and then starting to hold in that direction as you decelerate makes a single jump go further than it normally would. This is most useful for Juste before getting the double jump, and allows some jumps that would not otherwise be possible without the double jump.
Slide Momentum: Whipping after sliding off a ledge preserves the speed of the slide. It's only slightly useful for Juste before getting the double jump. If you really want to go off a ledge quickly, then it's better to whiplaunch, but this is a little faster in save rooms for example.
Fast Spellbook Navigation: You can press down+L+R to activate and deactivate spellbooks without the use of the pause menu and up+L or up+R to change spellbooks without the use of the pause menu.
Coyote Jumps: After moving off a ledge, you maintain your ability to use your grounded jump for your first 10 airborne frames. Doing so allows you to cross over most floor-based screen transitions with a low jump, crossing them much faster than using a full jump to get over them. This can also be used in tandem with ledge launches to cross some gaps that would otherwise need the double jump, as well as being the basis for getting the platinum tip early.
Whip Alternation: The game keeps track of different invincibility timers for enemies for different attacks, and it counts grounded whips and air whips as different attacks. Thus, it's faster to alternate between these attacks than it is to use just one. The basic sequence for this is Whip, Dash-cancel, Jump, Release Jump, Whip, Dash-cancel, Crouch-whip. With varying timing on dashes and crouching, you should be able to move around left and right while attacking the enemy. It takes some practice to do well, and is mostly useful for Juste at low level before the double jump, or when you want to kill an enemy without using magic or hearts.
Jump Memory: When you have the double jump, if your last jump before landing didn't use the double jump, then the next time you go off of a ledge you won't be able to divekick until you jump again. This means it might be faster to quickly do divekicks for no other reason just so you know you'll be able to divekick as soon as possible after going off of a ledge.
Jump Direction Lock: The game keeps track of two different going up and going down states during your jump. For Juste, these two have different sprites. When you go from going up to going down either at the top of your jump or from bumping a ceiling, the game will lock your speed for approximately 5 frames, though you can regain control by jumping again. This is really annoying when you expect to be able to change your movement in air but can't. On the other hand, this can be useful as an input buffer for some precise OoB movement.
Jump Heights: There are many different jump heights with different air times as listed following;
1 frame jump - 8 frames airborne, 4 pixel apex.
2 frame jump - 12 frames airborne, 7 pixel apex.
3 frame jump - 16 frames airborne, 11 pixel apex.
4 frame jump - 19 frames airborne, 14 pixel apex.
5 frame jump - 21 frames airborne, 17 pixel apex.
6 frame jump - 24 frames airborne, 20 pixel apex.
7 frame jump - 26 frames airborne, 23 pixel apex.
8 frame jump - 28 frames airborne, 26 pixel apex.
9 frame jump - 30 frames airborne, 28 pixel apex
10 frame jump - 32 frames airborne, 31 pixel apex
11+ frame jump - 59 frames airborne, 53 pixel apex.
Note: the apex jump heights were measured based on the top pixel of Juste's head and may not reflect his origin point for landing, will look into adjusting more accurately.