Hello Sean,

The main aim of IgxCombo is to combine an input with IgxDropDown. As you know IgxDropDown is a component which displays a scrollable list of items. Looking at your question you need a drop down which should display a tree structure. If this is what you need you should not use IgxCombo, neither IgxDropDown as you do not need a drop down with scrollable list of trees. What you can use is IgxToggle directive. If you are using a button to open and close the drop down your markup should look something like this:

<button igxButton="raised" igxRipple [igxToggleAction]="toggle">Open tree grid</button>
<div igxToggle #toggle="toggle">
 <igx-tree-grid #grid1 [data]="data" childDataKey="childDataKey" primaryKey="ID" [width]="'900px'" [height]="'500px'">
  <!-- Add your columns here -->
 </igx-tree-grid>
</div>

Please let me know if this is what you need or if you have any additional questions on this matter.

Looking at your picture it seems that you need tree component. Something like Material Tree. Right now we do not have such component. Implementing this in IgxCombo via custom item template will require a lot of custom logic like item expanding/collapsing; synchronize parent-child item selection and so on.

After working on this case having a tree has been determined as a new component idea. You can suggest new component idea for future versions by creating an issue in our public GitHub repository.

Thank you in advance to submitting your component idea.

www.infragistics.com/.../angular-dropdown-tree