GSGokul Sainarayanan Syncfusion Team January 28, 2020 07:58 AM
Thank you for contacting Syncfusion support.
We have checked your reported query and we can add the MultiSelectionComboBox in the RibbonControlAdv using the ToolStripControlHost. Please find the code snippet and the sample below. Please check and let us know whether it resolves your reported query.
Code snippet C# :
ToolStripControlHost controlHost = new ToolStripControlHost(multiSelectionComboBox1);