suggest me easy menu system in 16x2 lcd for uno board

there are tons of options... depends the complexity of what you want to do. an old timer one is at

30 main menu and 3 submenu for each is MenuBackend ok for this?

I just finished a menu system using a rotary encoder to walk through the options and the built-in encoder switch to select options. My system only has about a dozen options, but I quickly ran out of SRAM space and went to the new Mega2560 Pro Mini...smaller than an Uno, but a lot more memory resources. With all of the options you mentioned, you may need to consider it, too. You can find a link here:

econjack knows. I would avoid any menu system that relies in storing strings in RAM.

The best approach is to use the strings with F() and have only one "level" of menu data (aka strings) loaded at a time. No idea if there's a library that does that, thou.

Other issue is ow complex you wanted the menu to be. Do you want people to be able to enter numbers? Times?