CommonControls (Replacement of the MS common controls)

[Krool]

1. Is it possible to prevent Windows from overriding a ComboBox's BackColor when using CboStyleDropDownList? I set a combobox to &H00C0FFFF& (gold color) and Windows XP correctly shows all three ComboBox styles in gold, but Windows 10 only shows CboStyleDropDownCombo and CboStyleSimpleCombo in gold while showing CboStyleDropDownList in gray (probably from the Windows color scheme).

No, that's the visual style. If you want to to have a BackColor shown in CboStyleDropDownList then you need to set .VisualStyles = False.

2. Is it possible to programmatically disable the ComboBox drop-down animation? I wrote a routine to allow the user to search through a combo for a keyword and show only matching results. It works nicely in Windows XP where the drop-down shows instantly, but in Windows 10 the drop-down is animated and that makes searching slow.

I am not aware of a solution to a specific ComboBox.
If you want to avoid animation for the whole system consider using SPI_SETCOMBOBOXANIMATION.

3. When the mouse cursor hovers over the program window, Windows hides the mouse cursor when I call ComboBox.DroppedDown = True. That's very user-unfriendly. How do I prevent Windows from hiding the cursor?

After some research this is a "common" issue and described as a "very obscure set of circumstances".
The edit control in the ComboBox hides the cursor when entering a character. (just like a normal TextBox also does)
However, moving the mouse in an edit control resolves this issue.
But the drop-down list will set the "mouse capture" when it shows the drop-down portion.
Thus when the hCursor is NULL in that moment the mouse cursor will kept hidden.

I will encounter the issue more and will soon make an update to refresh the hCursor upon CBN_DROPDOWN in case it is NULL. (there is a solution for this)

4. Does the VBCCR ComboBox allow a better way of searching for partial matches at any point in the string than the way I did it?

A Virtual ComboBox is a perfomant use-case for such a "searching" functionality.
However, it might be better (considering the slow drop-down animation) to use the IAutoComplete interface.
It can be attached to any edit control. (= ComboBox1.hWndEdit)

Does anyone use the compiled version in VBA Excel professional environment with success ? (maybe few new happy users )

Do you mean 64bit or 32bit VBA ? Please note that VBCCR works only on 32bit VBA.