Critical fix: the tools no longer delete your materials.

Fill Controls, Apply Noise and the bake tools could remove every material on the active object except the first one. If you work with multi-material game assets, this is the update you want.

The cause was the channel viewer, not the fill tools themselves. Switching the viewer on took a snapshot of the object's material list; every later tool run forced the list back to that snapshot, deleting any slot added since and reverting any slot that had changed. The viewer now shows its preview through object-level slot overrides, so your material list is never written to at all.

Files damaged by an earlier version are repaired automatically when you open them in 1.3.0 — the original materials are restored.

Also fixed

• Objects no longer stay stuck showing the preview material after you select a different object.
• Float Color attributes, and color attributes stored per-vertex instead of per-face-corner, are now detected and written correctly. Previously the toolkit missed them and silently created a duplicate <name>.001 attribute, so your edits appeared to do nothing.
• Per-corner colour variation is preserved instead of being flattened.
• Materials are always left clean when the addon is disabled or another file is loaded.

Blender 5.x support

• Verified on Blender 4.5 LTS and Blender 5.2 LTS.
• Installs either as a classic add-on or as a Blender Extension (4.2+).
• Migrated off the deprecated vertex colors API to color attributes, replaced the Separate RGB node removed in Blender 5.0, and handled the EEVEE ambient occlusion settings that moved in 5.0.

Which file do I download?

• vertex_color_toolkit-1.3.0-extension.zip — Blender 4.2 and newer. Drag onto Blender, or Edit > Preferences > Add-ons > Install from Disk.
• UVCToolkit1.3.zip — classic add-on install, Blender 4.0+.

Both contain the same code.