Comment by wlonkly

You got me thinking, and this seems to work for me. I didn't test if the order of these blocks matters.

    [[on-window-detected]]
       if.app-id = "com.github.wez.wezterm"
       run = ["layout tiling"]

    [[on-window-detected]]
       if.app-name-regex-substring = '.'
       run = ["layout floating"]