12.3.1 is a small hotfix release for Substance 3D Designer.

Fixes
[3D Assets] 'Help > Substance 3D assets' mistakenly targets Creative Cloud Desktop on Linux
[3D View] Materials are not built when mesh is loaded
[3D View] Materials list opens when dropping Substance model graph in viewport
[Explorer] Cannot delete selection with keyboard if a Substance model graph is included
[Explorer] Crash when opening the contextual menu of a mesh resource's material item on Mac
[Graph] Instances whose Input images depends on Values generates wrong result in subsequent nodes
[Graph] Wrong result when using chain of subgraphs with contextual graph editing enabled
[MDL] Crash when loading MDL graph referencing a compositing graph with outdated outputs
[MDL] Texture 2D node does not work anymore
[Preferences] Image cache ignores the temporary files location set by the user
[Properties] Tweak performed in preview/preset panels are merged in undo stack
[Shortcut] Shortcut assigned on deprecated nodes create conflicts and can't be cleaned
[Substance models] Crash when closing a package after performing specific actions
[Substance models] Instance nodes and links from relocated packages are not refreshed correctly
[Substance models] Undoing deletion of subgraphs does not refresh instance nodes and links consistently
[Substance models] Value suddenly increases too fast on transform node
[UI] "Visible if" property warning icons does not have a tooltip
[UI] Image information text is too dark in 2D View's viewport
[Undo] Moving a position widget in preview mode stores all intermediate values

Improvements
[3DView] Optimized rendering for scenes with many materials
[3DView] View a Substance model graph's outputs when dropping it from Explorer
[Substance models] Display warning in Graph View when input and output share the same identifier