Misaki
I appreciate you trying to help me out, but as I said, this is not a problem without a workaround, it's more so about a blind spot in the editor's ability to offer a straight forward way to do something that, it can very much do but is locked behind a technicality (physics property can be read as negative if the animation's mix is negative, it's the fact the editor has a safety measure to prevent values below 0 from being entered, also for good reason, as mentioned).
Yes, physics can be manipulated through script, or in Spine by using sliders, or by setting the animation up for a negative mix. It's a matter of straight forward functionality, which I feel is in line with Spine's design as a lean and consistent well put together tool (which is the norm, to your hard work's credit).
As for specific cases, I'm sure it's on the rare side. I'll try to explain what I'm doing to give you an idea, sorry if it's long, it's a bit of a niche thing:
I have this monstrous design of a rig. This involves what would amount to a 3D character creator in a hyper-modular 2D format using many layers strategically broken down and stitched together parts connecting at very specific sections, adjustable and modular faces that retain custom shape before expressions, and all you'd expect: multi-part hairstyles, body proportion, multi-purpose meshes to integrate custom images into the rig. Then multi-layered outfits with full compatibility with all these changes, anything from jackets to earrings, hats, armor, dresses, capes, weapons... etc etc, gives you an idea, I don't think you'd want me to keep going as if this was some sort of pitch.
The animations themselves are also broken down and meant to be recombined. They work by parts, core movement, arm movement, background moods, gesturing, emotes, base stance type, etc, etc
All of this variability is able to function because animations do not use simple transforms but an abundance of "targets", used by constraints, typically transform and inverse kinematics. These mark safe positions where sections of the arms lock into, for contact, a specific pose (shushing, hands on hips, crossed arms) or not contact but consistent as the body shifts around (handled separately), Everything adapts to everything else, and it's worth the hassle because movement looks very fluid and natural.
So when I need to change proportion on something, be it an item, a body part, etc, it may or may not need to shift targets around, affect constraints, etc. And in turn, these targets and little modifications may or may not need to be tweaked by other variables and proportion changes. Meaning if I want to make the arms wider, it's not as simple as a scale transform on setup, it changes many things proportional to it, such as moving certain targets to offset poses, giving them more padding (which may also be affected by an outfit active there) In order to make posing/emotes and transitions smoother, avoid clipping as poses change, keeping variable distances stable (when a character is e.g clapping and the shoulders widen) and so on. So the simplest options are animations or sliders, these may or may not involve physics. On top of that, if they need to dynamically change within a specific animation, the prospect of handling by script is made far more inconvenient.
Now, because all graphics are at their or close to the max size to avoid pixelation/quality variation, and kept un-deformed in setup for potential mesh/rig modification, it means most of these modifications involve shrinking a group of bones instead of growing them (and moving tweaking relevant targets or applicable extra modifications), meaning physics (if relevant) needs to typically reduce in value.
It would simply be convenient if I could drop the physics key in here animation as well (as I had been doing before the changes), or you know, I can have a separate setting handled by script, tracking states and recalculating mixed stuff, or on a separate animation, or the same animation with a non-additive slider, there are many options.
Personally, I do not mind it in the slightest, it is a minor inconvenience and I'm no stranger to workarounds.
But the fact of the matter is that Spine can actually handle it, it can execute negative physics, it's just not able to set up a negative physics value on animations through the editor. I would consider this a minor design flaw.
Sorry for the long explanation, but as I said, I'm handling very specific challenges so I cannot give you a simpler example.
