Update README

README.md

@@ -69,7 +69,7 @@ If both `menu.dll` and `menu.lua` exists in scripts folder, one of it may be nam
 
 - `max_title_length=80`: Limits the title length in dynamic submenu, set to 0 to disable.
 
-## Updating menu from another plugin
+## Updating menu from script
 
 The menu data is stored in `user-data/menu/items` property with the following structure:
 
@@ -85,6 +85,8 @@ MPV_FORMAT_NODE_ARRAY
 
 Updating this property will trigger an update of the menu UI.
 
+To reduce update frequency, it's recommended to update this property in [mp.register_idle(fn)](https://mpv.io/manual/master/#lua-scripting-mp-register-idle(fn)).
+
 ## Credits
 
 This project contains code copied from [mpv](https://github.com/mpv-player/mpv).