Following @jk121960, and the caveats mentioned here, I've succeeded thus:
-- local hotkeys_popup = require("awful.hotkeys_popup")
local hotkeys_popup_jo = require("awful.hotkeys_popup");
local hotkeys_popup_jo_sized = hotkeys_popup_jo.widget.new({ width = 1000, height = 600 });
-- for my Lenovo IdeaPad 120s 81A4
myawesomemenu = {
--{ "hotkeys", function() hotkeys_popup.show_help(nil, awful.screen.focused()) end },
{ "hotkeys", function() hotkeys_popup_jo_sized:show_help(nil, awful.screen.focused()) end },
globalkeys = gears.table.join(
-- awful.key({ modkey, }, "s", hotkeys_popup.show_help,
awful.key({ modkey, }, "s", function() hotkeys_popup_jo_sized:show_help() end,