litee-calltree shows only first depth the call hierarchy, can we increase the layer of depth?

[hrcHarry]

Hi, I use nvim-lspconfig to attach clangd (which now does not provide incoming call and outgoing call) and ccls.nvim to attach ccls (which provides incoming call and outgoing call) coexisting with clangd.

In the configuration of ccls.nvim, incoming calls and outgoing calls are in the on_attach field as follows

local capabilities = require('cmp_nvim_lsp').default_capabilities()
local filetypes = { "c", "cpp", "objc", "objcpp", "opencl" }
local util = require "lspconfig.util"
local server_config = {
    filetypes = filetypes,
    init_options = { cache = {
        directory = vim.fs.normalize "~/.cache/ccls", -- if on nvim 0.8 or higher
    } },
    name = "ccls",
    cmd = { "ccls" },
    offset_encoding = "utf-32",
    root_dir = vim.fs.dirname(
        vim.fs.find({ "compile_commands.json", "compile_flags.txt", ".git" }, { upward = true })[1]
    ),
    on_attach = function()   -- !!! HERE !!!
                    vim.keymap.set('n', 'gce', vim.lsp.buf.incoming_calls, {desc = "Incoming calls", buffer = 0})
                    vim.keymap.set('n', 'gco', vim.lsp.buf.outgoing_calls, {desc = "Outgoing calls", buffer = 0})
                end,
    -- capabilities = capabilities,
    autostart = true,
}
require("ccls").setup {
    filetypes = filetypes,
    lsp = {
        server = server_config,
        disable_capabilities = {
            completionProvider = true,
            documentFormattingProvider = true,
            documentRangeFormattingProvider = true,
            documentHighlightProvider = true,
            documentSymbolProvider = true,
            workspaceSymbolProvider = true,
            renameProvider = true,
            hoverProvider = true,
            codeActionProvider = true,
        },
        disable_diagnostics = true,
        disable_signature = true,
        codelens = { enable = true }
    },
}

I encounter that the calltree of incoming calls and outgoing calls shows only the first call hierarchy, and I can not find the related configuration about depth in the doc (no matter in litee.nvim or litee-calltree.nvim).

How to fix that? Is there anything I miss?
Thanks.

[hrcHarry]

I think I find the way to expand the hierarchy. In the call tree panel, zo will expand the call hierarchy.