[Lazarus] where's the 'X'?

[waldo kitty]

for many years, i've used editors that allow for more than one file to be open 
at once... in those editors, there's generally been an 'X' to close that 
(sub)window containing each additional file... some editors have an 'X' for all 
files and closing the last one results in a new blank page...

with today's tabbed environments coming out and being all the rage, the 'X' has 
been moved to the tab for each file...

so anyway, the other day i'm working in laz and had a need to have more than one 
file open at the same time... when i was finished with the other file, i went to 
close it... i couldn't find the 'X'... there was the "big" main one for closing 
the entire laz IDE (ALT-F4) but not one for the individual files' windows... it 
took me a minute or two before i realized that i could right-click in that 
window and choose "close file" or i could use CTRL-F4 (which i have used in the 
past but not on a general basis and less as i get older)...

so anyway, my question is "where's the 'X' for closing each individual files' 
window?"