CLDR-17830 Update modifications section (#4081)

docs/ldml/tr35.md

@@ -4287,59 +4287,50 @@ Other contributors to CLDR are listed on the [CLDR Project Page](https://www.uni
 
 **Differences from LDML Version 45**
 
-* Part 4: [Dates](tr35-dates.md#Contents)
-  * In [Element dayPeriods](tr35-dates.md#dayPeriods), added a note on special formatting usable with
-    dayPeriods `noon` and `midnight`.
-
-**Differences from LDML Version 44.1**
-
-* Part 1: [Core](tr35.md#Contents)
-  * In [Parent Locales](#Parent_Locales), made substantial changes to the way that parentLocales work,
-    including a new attribute for algorithmic handling of inheritance
-    that avoids needing a long (and fragile) list of language-script codes
-    to skip when falling back to root.
-    That list was retained for migration, but will be withdrawn in the future.
-  * In [Special Script Codes](#special-script-codes), added a description of special script codes,
-    such as Jpan and Aran.
-  * In [Lateral Inheritance](#Lateral_Inheritance), improved the formatting for clarity.
-  * In [LocaleId Canonicalization:Preprocessing](#preprocessing), restructured the steps for clarity, added more examples.
-  * In [Likely Subtags](#Likely_Subtags), clarified that language subtags iw, in, and yi are treated specially in the data,
-    to allow for applications that use them as canonical language subtags.
-    Also removed the substitution for macroregions,
-    and noted that some elements could be NOOPs in customized data, but could be misleading.
-  * In [EBNF](#ebnf), added more differences from W3C EBNF,
-    and documented use of wfc: and vc: for wellformedness and validity constraints.
-    Marked clauses with that format where appropriate, and grouped constraints after the relevant EBNF.
-  * In [Element alias](#Alias_Elements), clarified the location to which the path in the `alias` element is relative.
-
-* Part 3: [Numbers](tr35-numbers.md#Contents)
-  * In [Supplemental Currency Data](tr35-numbers.md#Supplemental_Currency_Data), for the `currency` element,
-    added attributes `tz` and `to-tz` to clarify the `from` and `to` dates.
-
-* Part 4: [Dates](tr35-dates.md#Contents)
-  * In [Date Format Patterns](tr35-dates.md#Date_Format_Patterns), reserved date Pattern field lengths of greater than 16
-    as private use.
-
-* Part 6: [Supplemental](tr35-info.md#Contents)
-  * In [Mixed Units](tr35-info.md#mixed-units), clarified many aspects of mixed units (such as foot-and-inch),
-    including how to handle rounding and precision.
-  * In [Testing](tr35-info.md#testing), listed the additional test files.
-  * In [Unit Preferences Overrides](tr35-info.md#Unit_Preferences_Overrides), made substantial changes including
-    handling of edge cases, such as where there is no quantity for a unit, or no preference data for a quantity;
-	how to handle invalid subtags;
-	negative unit amounts;
-	the usage of each of the subtags that affect unit preferences, and others.
-  * In [Conversion Data](tr35-info.md#conversion-data), added the `special` attribute for `convertUnit`, used for handling beaufort.
-  * In [Unit Prefixes](tr35-info.md#unit-prefixes), added the SI unit prefixes and the power of 10
-    (or 2, for binary prefixes) that they represent.
-
-* Part 7: [Keyboards](tr35-keyboards.md#Contents)
-  * Added substantial changes from v44 to bring the Keyboard 3.0 specification out of Tech Preview, including:
-    * New sections for Definitions, Notation, and Normalization.
-    * Many clarifications and modifications in other sections.
-
-* Part 9: [MessageFormat](tr35-messageFormat.md#Contents)
-  * Added the completely new specification for MessageFormat 2.0 (in Tech Preview)
+### Conformance Modifications
+
+Updates to [LDML Conformance](#Conformance) including
+- clarification of conformance requirements
+- an expanded list of major sections
+- details about customization
+- a summary of conformance data files
+
+### Locale Identifiers and Inheritance Modifications
+- Clarified definitions of _Unicode BCP 47 locale identifier_ and _Unicode CLDR locale identifier_, moving them to [Unicode CLDR locale identifier](#unicode-locale-identifier)
+- Clarified useage of [Special Script Codes](#unicode-locale-identifier).
+- Added definition of [Ordered Elements](#definitions), replacing the obsolete definition of _blocking_ elements.
+- Clarified the usage of the `path` attribute with [aliases](#element-alias).
+
+### Message Format Modifications
+
+Significant updates to [Message Format](tr35-messageFormat.html#Contents) 
+- Removed all of the reserved and private use syntax constructs, simplifying the grammar.
+- Changed the structure of the .match (selector) to require use of local or input declarations. This is a breaking change for existing messages.
+- Added support for bidirectional isolates and marks and clarified whitespace handling to better enable messages that contains right-to-left identifiers and text.
+
+### Date Modifications
+- Added a tech preview section on [semantic skeletons](tr35-dates.html#Semantic_Skeletons), allowing for less data and faster performance in formatting dates.
+- Clarified that if [dayPeriods](tr35-collation.html#grouping_classes_of_characters) are specified for `noon` and `midnight`, they can often be formatted without also specifying the numeric time
+- In [Element dayPeriods](tr35-dates.html#dayPeriods), added a note on special formatting usable with dayPeriods `noon` and `midnight`.
+
+### Units Modifications
+- Changed the EBNF for [`unit_identifier`](tr35-general.html#Annotations):
+    - Replacing  `number_prefix` by [unit_constant](tr35-general.html#syntax) to generalize expressions like liter-per-100-kilometers, and provide a compact form for longer constants (such as 1e9).
+    - Adding EBNF constraints on `si_prefix` and `binary_prefix`, and adding links to more named components.
+- Clarified the use of -rg for [computing regions](tr35-info.html#compute-regions) in user preferences
+
+### Collation Data Changes
+- Modified [Grouping classes of characters](tr35-collation.html#grouping_classes_of_characters) to reflect two major changes.
+    - The [CLDR root collation](tr35-collation.html#Root_Collation) is a tailoring of the [DUCET](https://www.unicode.org/reports/tr10/#Default_Unicode_Collation_Element_Table).
+Changes have been made to both to align them better:
+        - non-decimal-digit numeric characters now sort after decimal digits
+        - the CLDR root collation no longer tailors any currency symbols (making some of them sort like letter sequences, as in the DUCET). 
+    - Starting with CLDR 46, the CLDR radical-stroke order matches that of the [Unicode Radical-Stroke Index (large PDF)](https://www.unicode.org/Public/UCD/latest/charts/RSIndex.pdf).
+[Its sorting algorithm is defined in UAX #38](https://www.unicode.org/reports/tr38/#SortingAlgorithm).
+
+### Misc. Modifications
+- Clarified the usage model for [emoji search keywords](tr35-general.html#Annotations).
+
 
 Note that small changes such as typos and link fixes are not listed above.
 Modifications in previous versions are listed in those respective versions.