The multi-column dropdown functionality works great, but what would I add/change to make it so that the dropdown goes away when the dropdown arrow button is clicked a 2nd time so that it behaves more like a normal combo box?

I assume (and hope) it would be a simple change to the provided MultiColDropDownList class and not something I would add to my own code, but I wouldn't know what to change.

Is there something simple I can adjust to achieve this?
If you click outside of the drop-down list, the list is closed. However, if you click another cell, this cell becomes selected. And I think you want to close the drop-down list without changing the current cell because of this when you click the combo button - right?

If yes, then I can say that this improvement was suggested by others too and it is in our to-do list. Maybe, not in the iGrid.NET X release, but definitely in the next minor update.

I am moving this suggestion to the corresponding section with suggestions.
Correct. Sometimes people want to just open the dropdown box to see the options, and then expect to be able to click the drop down arrow again to close it without worrying about accidentally changing things by having to click on something else to close it.
There is one more related thing. Do we need to change the cell selection if the user clicks outside of the cell with the drop-down list?
In my opinion, the dropdown works perfectly the way it is when it comes to which item is selected when the user clicks in a different cell. The only addition I would make is for the dropdown grid to be "closed" when the user clicks the dropdown arrow while it is open.

So see this behavior, just place a normal combo box on a form, fill it with some items, and click the drop down arrow, which displays the list, and then click the arrow again, and the list goes away. That's all I am suggesting.