`place-self` still requires the parent to be a flex-box container, though. You can't just apply it to an arbitrary element to make it center in its parent.
`place-self` is just shorthand for setting both `align-self` and `justify-self` in a single proeprty - I don't see how this is necessarily an improvement: CSS is already (unfortunately, necessarily) confusing at it is, so adding a literally redundant CSS property with a distinct name is not going to reduce confusion nor make CSS any more accessible.
CSS's shorthand properties work best when the shorthand version actually aids comprehension, rather than making you think: for example, `border: <width> <style> <color>;` and `margin: <top> <right> <bottom> <left>;` are great examples of how they should be: either because each parameter is unambiguously typed (in `border`'s case: widths, border-style and colors are very distinct) or uniformly-typed but follow a familiar pattern (e.g. `margin:`'s parameters are all length-values but are in a clockwise sequence) - this is not something we see in some of the more modern shorthand properties like `flex` and `box-shadow` where you need to have pre-memorized which parameter corresponds to each longhand property, e.g. it's non-obvious that the `2` in `flex: 1 2 3px` is for `flex-grow` - or that the `3px` in `box-shadow: 1px 2px 3px 4px rgba(0,0,0,0.2);` is for `blur-radius` and not `spread-radius`.
> It’s good to see that the problem of anchoring tooltips is progressing through this process!
I'm also strongly in favour of this CSS feature, it's a long-time coming - BUUUUT I also really would have liked some browser-native tooltip/title feature that allows for rich-content without resorting to hacks like `foo[title]::after { position: absolute; content: attr(title); etc }`