Button spacing and spacers
Currently the buttons in TC have no spacing at all. This makes spotting buttons different as they are somewhat squeezed. A reasonable spacing should be a few pixels (considering DPI settings and button size).
Flexible spacers are known from other programs like Firefox. Using flexible spacers let users group buttons very nicely (better than fixed separators). It works like this: The buttonbar contains 20 buttons which are seperated into three groups (two spacers used). The first group would be left aligned, the second centered and the third is right-aligned. So the distance betwenn the groups is distributed equally between the groups. Example groups can be distinct things such as internal commands, program launches or directory changes.