Issue description

Currently, tmux has via send-keys -X rectangle-toggle the ability to toggle rectangle selection on and off. When a selection is already active, toggling rectangle selection on behaves very much like toggling on visual block mode in vim: the rectangular selection is based off of the original selection.

Tmux also has send-keys -X select-line. When starting a brand new selection, this behaves like visual line mode in vim. However, when a selection is already active, the select-line command ignores the previous selection and selects instead the line that the cursor is currently on.

It would be nice to have the ability to toggle "line selection" on and off.

Required information

$ tmux -V
tmux 3.2a