Experimenting with New Transform Constraint
You're right that sliders are similar to transform constraints. Sliders map a bone value to animation frames.
I didn't quite understand this part:
The current mix of slider constraints is used to control the mixing of animations, not the mixing between bones and timeline maps
The slider mix is between the current pose and the pose from the slider's animation. It is only sort of mixing animations. It's better to think of sliders differently from animations. You don't really want to use sliders to mix animations. For that you should use the Preview view (AnimationState at runtime). For example, if your character is holding a burning torch, you wouldn't use a slider. You would play an animation so the torch burning animation is always playing.
Sliders sort of abuse an animation to allow you to apply a pose. Sliders can sort of "play" and mix animations, but it doesn't have the control you get with AnimationState. Sliders are best for storing poses and rigging that needs poses. There are many uses though, I'm sure you guys will come up with crazy new stuff!
We could have a match button, though it would only be able to set the bone from minimum value. The only problem is there's not a great place in the UI to locate it. 
Was there another suggestion you had beside the match button?
I see, thanks for the explanation!
With a transform constraint you can either set the mix or edit the mapping numbers to control how much affect the transform constraint has. Setting the mix is easier, but it can be convenient to use the mappings because then you can animation 0 to 100% mix to get the effect you want. Otherwise you have to remember to key the mix eg 0 to 53.76%.
A slider's mix works exactly the same way as the transform constraint, so you can use it to control how much effect you get from the slider. Other ways to change the magnitude of the slider effect is to change the mapping numbers or edit the animation keys or animation duration.
If we had another setting on the slider for controlling how much of an effect you get, what would it do? That sounds like the same thing mix does. If you have an animation that moves a bone, you can set a mix < 100% to move it less or > 100% to move it more.
Here's an interesting setup to think about, magnetic IK!
Very nice! 
️ 4.3 setups can seem like magic the first time you see them!
You can probably use 2 sliders, one for X and one for Y, with additive set.
Nate 在休假中、没有关注新特性。(停留在4.3.16)
研究了一下大概是这个样子？
不清楚是那个版本新添加的滑块约束动画帧可以映射到某个骨骼的变换属性上。
新功能能实现很多有趣的想法。但是好像变得更加复杂了(指理解和学习成本)
很多时候理解原理但是可能习惯直接键帧似乎、、
Looks like you got it! For everyone else: a slider animation controls the IK mix. When the slider's bone enters the range, the IK is turned on, when it leaves the range it is turned off.
These setups are definitely more complex than just setting keys. Mostly we are just exploring the new tools. In the real world you would have some goal, then hopefully you use the advanced setups only when warranted. We see far too many projects that have literally 500 or even 1000 constraints, and that's before sliders and the new transform constraint. Please don't do that! 
If you've missed the last few updates, check the changelog. The update today was very important, I posted about it here:
https://esotericsoftware.com/forum/d/28555-4317物理约束出现奇怪的形为/20
Voice-of-Shadow 啊明白了感谢感谢！
Voice-of-Shadow WHAT?! Did you create constraint by dragging and releasing a bone on another?
I think he used a hotkey, then clicked the target bone. Hotkeys are fast!
Soon! Sorry about that, just got busy with many things. 
Voice-of-Shadow
我感觉这个才是官方的做法，它x进出的时候才会完全吸附或者离开
你x离开的时候，y还附加在上面
