Hi, I'm playing on the most recent update (2.4) and i seem completely unable to use the Z level function of the game. Whenever I do the game essentially freezes until I open a menu (like inventory, or esc menu) and then I can move again, but i don't travel a Z level. 

Is this a feature to be added in later or am I missing something?

This sounds super weird as I can go up and down stairs without an issue and even pressing z at random intervals doesn't cause anything like you describe for me. You're standing on top of the stairs (tile being '<' or '>') and pressing z?  Maybe some files didn't download correctly? If you go to your game's directory (I'm not sure where it is on itch launcher I've been using direct download) and go to 'Data > Designs' pretty sure these are the zone map files, any of them that don't end in 0 but end in 1 or -1 are maps that are up or down from the base world Z levels. I would check that those are actually there and not corrupted and filled with nonsense. They should start with like

{
    "design": {
        "cereal_class_version": 0,
        "value0": "Slums",
        "value1": 0,
        "value2": 0,
        "value3": 0,
        "value4": [
            [
                [
                    1
                ],
                [
                    1
                ],
                [

and go to something like

           ],
                [
                    30,
                    9
                ],
                [
                    30,
                    7
                ],
                [
                    30,
                    7
                ],
                [
                    30,
                    7
                ],
                [
                    30,
                    9
                ],
                [
                    30,
                    7
                ],
                [
                    30,
                    7
                ],
                [
                    30,
                    7
                ]
            ]
        ],
        "value5": [
            [
                false,
                false,
                false,
                false,
                false,
                false,
                false,
                false,

Any particular place the z key resulted in freeze? The freeze is usually an indicator that there is some infinite loop going on, there might be some rare conditions you have that caused that. If you could send me a zipped save folder located at C:\Users\<your_user>\AppData\Roaming\WizardsOfTheCode\Soulash\saves\1 it would help me find out what's going on. If possible send it to support@wizardsofthecode.pro

The design maps are used to generate the world at new game, but during play the actual maps are inside the save folder so everything can be persistent.