First, thank you for evaluating r.a.d.controls
for WinForms and I would like to say that your feedback is of great importance to us.
When saying "the toolstrip dropdown menu" do you mean the ToolStrip OverFlow Button (the button appearing at the rightmost which dropdowns a list of checkboxes which hide/show the ToolStrip elements) or do you mean a DropDownButton which is inserted in the ToolStrip.
In case you have in mind a DropDownButton inserted in a given ToolStripElement you can insert custom items/elements/controls in its dropdown using several approaches.
If you would like to insert a checkbox item for example in the DropDownButton Items collection you can use the following code:RadMenuContentItem contentItem = new RadMenuContentItem();
RadCheckBoxElement checkBox = new RadCheckBoxElement();
contentItem.ContentElement = checkBox;
You can insert a DataGridView control for example in the DropDownButton Items using a RadHostItem
:RadMenuContentItem contentItem = new RadMenuContentItem();
DataGridView gridView = new DataGridView();
RadHostItem hostItem = new RadHostItem(gridView);
contentItem.ContentElement = hostItem ;
I hope this information helps.