Getting error on load.
prototype "toggle-waypoint-mod" (shortcut) Value must be a string in properety tree atROOT.shortcut.toggle-waypoint-mode.icon

updated

Still getting the same error even after the update https://imgur.com/a/p6koCtE

The shortcut prototype is missing the required 'small_icon' property. Factorio shortcuts require both 'icon' and 'small_icon' to be defined. Simply add a small_icon property pointing to your icon file to fix the error."

data:extend {
    {
        type = "custom-input",
        name = "build-transport-line",
        key_sequence = "CONTROL + mouse-button-1"
    },
    {
        type = "custom-input",
        name = "build-transport-line-no-underground",
        key_sequence = "CONTROL + SHIFT + mouse-button-1"
    },
    {
        type = "custom-input",
        name = "build-transport-line-prefer-ground",
        key_sequence = "CONTROL + ALT + mouse-button-1"
    },
    {
        type = "custom-input",
        name = "select-line-starting-point",
        key_sequence = "CONTROL + mouse-button-2",
        alternative_key_sequence = "CONTROL + SHIFT + mouse-button-2"
    },
    {
        type = "custom-input",
        name = "toggle-waypoint-mode",
        key_sequence = "CONTROL + Q",
    },
    {
        type = "custom-input",
        name = "terminate-path-finding",
        key_sequence = "CONTROL + SHIFT + T",
    },
    {
        type = "shortcut",
        name = "toggle-waypoint-mode",
        toggleable = true,
        icon = "__BeltRouter-lite__/icon/waypoint-mode.png",
        small_icon = "__BeltRouter-lite__/icon/waypoint-mode.png", 
        action = "lua"
    }
}

Here's the fix.

Which, does get you to the main menu but there is a bigger problem:

__BeltRouter-lite__/MiscLib/path_find/path_node.lua:6: module assert_not_null not found;  no such file __BeltRouter-lite__/MiscLib/path_find/assert_not_null.lua no such file __BeltRouter-lite__/assert_not_null.lua no such file __core__/lualib/assert_not_null.lua
stack traceback:
    [C]: in function 'require'
    __BeltRouter-lite__/MiscLib/path_find/path_node.lua:6: in main chunk
    [C]: in function 'require'
    __BeltRouter-lite__/transport_line_connector.lua:25: in main chunk
    [C]: in function 'require'
    __BeltRouter-lite__/control.lua:21: in main chunk

Which, does get you to the main menu but there is a bigger problem:
lua __BeltRouter-lite__/MiscLib/path_find/path_node.lua:6: module assert_not_null not found; no such file __BeltRouter-lite__/MiscLib/path_find/assert_not_null.lua no such file __BeltRouter-lite__/assert_not_null.lua no such file __core__/lualib/assert_not_null.lua stack traceback: [C]: in function 'require' __BeltRouter-lite__/MiscLib/path_find/path_node.lua:6: in main chunk [C]: in function 'require' __BeltRouter-lite__/transport_line_connector.lua:25: in main chunk [C]: in function 'require' __BeltRouter-lite__/control.lua:21: in main chunk

updated, but still has issue

After a long time spent identifying and fixing the issue,

the problem has finally been resolved.

I'm exhausted!

Please feel free to use it again soon.