Here's a (very hand-wavy) list of features I believe could be added to the "Safe to Release pre-CR Exceptions" section of CSS 2024:

Typographic pseudo-elements, ::before, ::after from CSS Pseudo-Elements 4 (basically all from CSS 2 with double-colon syntax plus ::prefix and ::postfix)

• Spec. status: WD (last published: 27 June 2025)
• Implemented in all major browsers for many years
• WPT: passing tests: Chrome: 3, Edge: 3, Firefox: 3, Safari: 3; interop: 3 / 3 (100.0%)
• Open issues: on GitHub: ~14, in spec.: 0

All from CSS Animations 2

• Spec. status: WD (last published: 2 June 2023)

font-tech() and font-format() from CSS Conditional 5

• Spec. status: WD (last published: 5 November 2024)
• no issues regarding them
• implemented in all major browsers since 2023
• WPT: passing tests (font-format(), font-tech()): Chrome: 9, Edge: 9, Firefox: 9, Safari: 9; interop: 9 / 9 (100%)
• Open issues: on GitHub: 1 (only editorial), in spec.: 0

:is(), :where(), :has(), and selector lists in :not() from Selectors 4

• Spec. status: WD (last published: 11 November 2022)
• Implemented in all major browsers since 2021 and :has() as part of Interop 2023
• Selectors 4 was also added to "Rough Interoperability"
• WPT: passing tests: Chrome: 2231, Edge: 2231, Firefox: 2208, Safari: 2158; interop: 2150 / 2261 (95.1%)
• Open issues: on GitHub: ~12, in spec.: 0

conic-gradient() and <color-interpolation-method> for gradient functions from CSS Images 4

• Spec. status: WD (last published: 17 February 2023)
• Implemented in all major browsers
• WPT: passing tests: Chrome: 2512, Edge: 2618, Firefox: 2825, Safari: 2874; interop: 2435 / 2948 (82.6%)
• Open issues: on GitHub: ~9, in spec.: 3

linear() from CSS Easing 2

• Spec. status: FPWD (published: 29 August 2024)
• see also [css-easing-2] Is linear() easing in a shippable state? #7533
• implemented in all major browsers since 2023
• WPT: passing tests (experimental): Chrome: 29, Edge: 29, Firefox: 29, Safari: 40; interop: 28 / 41 (68,2%)
• Open issues: on GitHub: 1, in spec.: 0

transition-behavior property, @starting-style rule and CSSStartingStyleRule interface of CSS Transitions 2

• Spec. status: WD (last published: 5 September 2023)
• Implemented in all major browsers as part of Interop 2024
• WPT: passing tests: Chrome: 60, Edge: 60, Firefox: 59, Safari: 60; interop: 59 / 60 (98.3%)
• Open issues: on GitHub: 6, in spec.: 0

text-decoration-thickness, text-underline-offset properties and from-font value for text-underline-position from CSS Text Decorations 4

• Spec. status: WD (last published: 4 May 2022)
• Implemented in all major browsers since 2021 and earlier
• see also [css-env] Publish FPWD? #6729
• WPT: passing tests (experimental): Chrome: 228, Edge: 228, Firefox: 345, Safari: 179; interop between Chrome, Edge, and Firefox: 228 / 345 (66.1%)
• Open issues: on GitHub: 2, in spec.: 1

env(safe-area-inset-*) from CSS Environment Variables 1

• Spec. status: ED (requires to publish a FPWD)
• implemented in all major browsers since 2020
• WPT: passing tests (experimental): Chrome: 42, Edge: 42, Firefox: 37, Safari: 37; interop: 37 / 42 (88.1%)
• Open issues: on GitHub: ~5, in spec.: 5

accent-color property, auto value for outline-color property, and <url-set> value for the cursor property from CSS UI 4

• Spec. status: WD (last published: 16 March 2021)
• accent-color implemented in all major browsers (partially in Safari) since 2022, auto value implemented in Safari, <url-set> implemented at least in Firefox since 2021
• WPT: passing tests: Chrome: 483, Edge: 483, Firefox: 482, Safari: 488; interop: 482 / 490 (98.3%)
• Open issues: on GitHub: ~5 (1 editorial), in spec.: 0

All from CSS Highlight API 1

• Spec. status: WD (last published: 15 December 2021)
• Implemented in all major browsers
• WPT: passing tests (experimental): Chrome: 237, Edge: 238, Firefox: 183, Safari: 188; interop: 175 / 241 (72.6%)
• Open issues: on GitHub: 17, in spec.: 3

text-box-trim and text-box-edge from CSS Inline Layout 3

• Spec. status: WD (last published: 18 December 2024)
• experimentally implemented in Safari, Chrome, and Edge
• WPT: passing tests (experimental): Chrome: 252, Edge: 252, Firefox: 66, Safari: 238; interop between Chrome, Edge, and Safari: 198 / 294 (67.3%)
• Open issues: on GitHub: 17, in spec.: 2 (1 editorial)

All from CSS Overflow 3

• Spec. status: WD (last published: 29 March 2023)
• Implemented in all major browsers
• WPT: passing tests: Chrome: 1338, Edge: 1324, Firefox: 858, Safari: 816; interop: 686 / 1424 (48.2%)
• Open issues: on GitHub: 50, in spec.: 5

All from CSS Paged Media 3

• Spec. status: WD (last published: 14 September 2023)
• Implemented in all major browsers
• WPT: passing tests: Chrome: 349, Edge: 339, Firefox: 249, Safari: 122; interop between Chrome and Firefox: 212 / 401 (52.9%)
• Open issues: on GitHub: 35 (2 editorial), in spec.: 2

Several of the interfaces defined in CSSOM 1

• Spec. status: WD (last published: 26 August 2021)
• Implemented in all major browsers for many years
• WPT: passing tests: Chrome: 3836, Edge: 3836, Firefox: 3842, Safari: 3692; interop: 3596 / 3949 (91.1%)
• Open issues: on GitHub: 150, in spec.: 19

(I believe should be cut now regarding its feature set and a CSSOM 2 spec. started for new features, see #10686.)

For this list I went through all the specs and checked what seems fairly stable to me based on issues within the spec. and on GitHub and/or is already widely implemented in browsers. For some I checked the WPT coverage, though not all. I may go through them and provide some more detailed info. And there are surely some Interop 2023 and 2024 features I didn't list here yet, which might be added.

Everyone is encouraged to edit this list or suggest additions, changes, or removals! And let me know if it makes sense to split it into separate issues to discuss them individually!

Sebastian