I don't think one line on screen with menu is too much ;-)
To your second request - this is a standard Open dialog function. Enter your mask on file name field and press Enter. You will see only files you need. You can select all your files and open it in one step. In PSPad File explorer you can set filter too -- <http://forum.pspad.com/read.php?2,49002,49010> PSPad freeware editor http://www.pspad.com
