Tmux 2: Main pane smaller than other pane with select-layout main-horizontal

Title: tmux 2: Main pane smaller than other pane with select-layout main-horizontal (p. 39)

Using tmux 3.2a, alacritty 0.11.0-dev terminal emulator, linux mint 20.2 cinnamon.

When running script development on p. 39, the main window on top is smaller than the one on bottom, contrary to expected results of using the main-horizontal layout. Additionally the welcome screen of Vim/Neovim (tried both in script) gets wiped out and when I open a file in Vim/Neovim, such as the development script, the command line of Vim/Neovim does not clear after using “e ~/development” to open development in editor.

If I try to run the commands manually line-by-line this undesired result always occurs at the point “select-layout main-horizontal” is run in the tmux command line.

Any thoughts?

Thanks in advance!
boB Stepp