Additionally to the channel filter at the top of the list, there is a text filter you can use to help narrow down the number of channels displayed in the Active Channel list.

It filters the active channels in the above list that have the same beginning letters as typed in the text box. If the text box is empty all objects get displayed. If you type in a "C" i.e. only objects that name begins with a "C" - like Camera 1, Camera 2 etc. will be listed in the Object Selector. The text entry is case sensitive.