Help file from TC wrote:Configuration - Quick Search
Quick search in current directory
CTRL+ALT+Letters The quick search window is opened with CTRL+ALT+Letter. Once the window is open, the CTRL and ALT keys can be released. The ALT key together with a letter activates the menu item which is underlined.
ALT+Letters With this setting, ALT+Letter activates the quick search window. The menu can be activated with F9, F10 or ALT - release ALT - Letter.
Letter only Like in file manager/Explorer, typing a letter jumps to the next file starting with that letter. To use the command line, you must press the right cursor key, or shift+right key if brief file display is on. You can type the first few characters of a file, not only the first lettter. Total Commander will 'forget' the typed letters after about 1 second delay.
I think, that it is a good idea to enable quicksearch by extention with ctrl+alt pressed , when letter only or alt mode for quicksearch by name is activated and vice versa. It could be optional. Configuration - Quick Search window has enough place to put new radiobuttons or checkbox.