New:
- Isolate Selected in Edit Guides is now a reversible visibility layer with a hotkey, and the previous permanent behavior is available as Hide Unselected (#7253)
- Added a Match Strand Groups option to Adopt External Guides, so each hair strand follows only the control guides of its own strand group (#6862)
- Added a Concatenate Strand Groups option to Merge, which renumbers each merged object's strand groups so they cannot overlap (#7269)
- Even clump distribution can now be used together with a distribution map
- Guides created with the Create brush and strands drawn with the Draw Strand tool now inherit the strand group and other data of the closest guide, with per-data options (#7138, #7139, #7142)
- The last selected Edit Guides brush is remembered instead of falling back to Comb (#5053)
- Parameter rollouts now enable and disable their controls based on other parameter values (#7242, #7245, #7246)
- Groom files are smaller through binary storage of mesh face indices (#7209)
- The Ornatrix V-Ray plugin is now deployed into V-Ray Standalone (#3973)

Fixed:
- Crash when an operator enables guide dependencies on hair which has none (#7109)
- Baked hair not being loaded from its source file after a scene is loaded (#7110)
- Strand Multiplier assert in Reinterpolate when its change cache is enabled (#7249)
- Remembered root positions not disabling the distribution controls (#7250)
- Hair from Guides regenerating roots on every evaluation when a distribution map is assigned (#7068)
- Deleting a strand created by the same guides delta in Edit Guides (#7059)
- Hidden guides reappearing on the next evaluation (#7255)
- Adopt External Guides ignoring the control guides when the three nearest ones are collinear (#7108)
- Per-clump and pattern knot parameters not taking effect until the groom was reloaded (#7147)
- Clumping assert when Use UV Space names a mapping channel the hair does not have (#7244)
- Merged ungrounded strands and merge target strands being moved to the first distribution mesh face (#7221, #7224)
- Merged strands grounded to a different distribution mesh being re-planted (#7223)
- Dynamic grounding failing when no source surface is set (#7226, #6819)
- Mesh from Strands crash with Conform to Surface when the distribution mesh is carried only by the hair (#7213)
- Cap Ends breaking the Mesh from Strands output (#7322)
- Meshes exported to Alembic having inverted face winding (#7327)
- Groom script parameter values being lost on scene save and reload (#7219)
- Groom scan recursing until stack overflow when a groom references a graft surface missing from its directory (#7325)
- Create Groom assert when the graft grooms cache file cannot be removed (#7241)