Tested with the latest snapshot of 3.9 (qds dev based). Possibly an issue in 3D projects (created with wizard's 3D template) only -> at least I was not able to reproduce with general projects.

Steps to reproduce:

• Launch DS
• Create a new 3D project
• Click + in Components
• ->Some modules are missing in the list.
• on macOS the missing modules are:
  • QtQuick.Layouts
  • QtCharts
  • QtDataVisualization
  • QtMultimedia
  • QtQuick.Studio.Application
  • QtQuick.Timeline
  • QtQuick3D.AssetUtils
  • QtQuick3D.Particles3D
• on windows the missing modules are:
  • QtQuick.Layouts
  • QtQuick.Studio.Components
  • Qt.Quick.Studio.Effects
  • QtQuick.Studio.LogicHelper
  • QtQuick.Studio.Multitext
  • QtQuick.Controls.Windows
  • QtQuick.Studio.Application
  • QtQuick.Timeline
  • QtQuick.AssetUtils
  • QtQuick3D.Effects
  • QtQuick3D.Helpers
  • QtQuick3D.Particles
  • QtQuickUltralite.Extras
  • QtQuickUltralite.Layers
  • SimulinkConnector
• After closing and reopening the project, import list shows all possible imports correctly