I use a tiling window manager (awesome) + a terminal multiplexer (tmux) + splits inside of vim. I have no window decorations at all, so you there is no visual split between them at all if the content of the program doesn't give it away. I'm quite comfortable with this paradigm as I use multiple monitors and group tasks by screen anyway. If two windows didn't have a reason to be side by side they wouldn't be there in the first place.However this creates a bit of visual dissonance where the most obvious split visually is the least significant semantically.Xorg window | window = nothing at allTmux pane | pane = 1px divider lineVim split | split = 1 character wide colored columnHere's a sample showing one each side by side windows, panes and vim splits:Even without clicking through to the full resolution version, the white divider line you see is the least significant split on the screen, the vim panes. (Note the gray column at the right of the vim session is actually an 80th column highlight, not a divider of any kind although I do often work at that size.)I am aware of how to change the character drawn in the split or reduce the color scheme contrast. What I would like to do is use the same split bar as tmux that doesn't take up any width because it's drawn in between columns rather than in one. Is this possible with terminal based vim? Gvim? Neovim? Baring making a visually unobtrusive separator, can the divider column be turned off entirely?P.S. The reason using a visually similar separator makes sense is because I use the same key-bindings to navigate between tmux panes and vim splits. The same keys navigate seamlessly between them, it would only make sense if the visual boundaries were the same as well.
Can the split separator in vim be less than a full column wide?
split;terminal;highlight
You are wrong about tmux. Like every terminal-based program  including Vim  it only draws stuff inside cells. This means that Vim and tmux both use the same method to draw vertical borders: they just use a pipe-like character.Tmux uses  (U+2502) by default while Vim uses | (U+007C).If you want the same separator in Vim, you can simply use the same character:set fillchars+=vert:Note that your colorscheme probably sets the background-color of the vertical split. If that's the case, you can remove the background-color directly in your colorscheme:hi VertSplit ctermbg=NONE guibg=NONE