See also #4632.

This was in the spec but hasn't been implemented yet. Basically just wt ; split-pane -% 30 cmd to open the Terminal with two panes, one that's 70% of the available size, and the other that's got 30%.

Or wt ; split-pane -% 30 cmd, split-pane -% 70 wsl for three panes, one with 70/30 split, and the 30 is then split into 30/70, kinda like:

+-------------------+-------+
|                   |       |
|                   |       |
|                   +-------+
|                   |       |
|                   |       |
|                   |       |
|                   |       |
|                   |       |
|                   |       |
+-------------------+-------+