outline with positon left shows no preview window

Describe the bug

When I set the win_position to left, I can not see the preview window:

Enven when I close the nvim-tree, I cannot see the preview window either:

Besides, I wonder how to set the windows at the left of the nvim-tree or aside left with current buffer.

Steps to reproduce

lspsaga config:

require('lspsaga').setup({

    outline = {
        win_position = 'left',
        keys = {
            jump = '<cr>',
            toggle_or_jump = 'o',
            quit = { 'q' }
        }
    },
    code_action = {
        keys = {
            quit = { 'q', '<esc>', '<c-n>' },
            exec = '<cr>'
        }
    },
    diagnostic = {
        keys = {
            quit = { 'q', '<esc>', '<c-n>' },
            quit_in_show = { 'q', '<esc>', '<c-n>' },
        }
    },
    hover = {
        open_cmd = '!wslview'
    },
    rename = {
        keys = {
            quit = { '<esc>', '<c-n>' }
        }
    }
})

Expected behavior

The outline window is attached to current buffer at lfet.

Neovim version (nvim -v)

0.10.0

lspsaga commit

6f920cfabddb9b7de5a3a4d0b7cd4f0774ae23e2

Terminal name/version

wt

Reproduce the issue from the provided lspsaga setup, focusing on outline.win_position = 'left' with and without nvim-tree. Start by tracing the outline window entry point and its left-position handling. Done means the outline preview is visible to the left of the current buffer, with behavior matching the expected placement.