Resize 'open' window in KDE programs
 

Got Debian+Fluxbox and when I choose (file) open in programs like ARK or Kate I get a a very small window and I can hardly see the file/folders.
How do I resize it?

grab the lower right corner with your mouse and click the left button, pull to the size you want. once it's that size, right click on the top of the window and choose "remember" and "dimension"

It doesn't work in the mentioned programs.
I get a "normal" mouse icon and nothing happenes when I hold the left button and try to resize.
that's the reason I asked the question.