Python - How to rename duplicated keys in a nested 'dict' while keeping their order

Question

I'm curious how one would go about renaming duplicated key names in a Python dict containing potentially multiple nested dicts.

I have a dictionary that will be used to dynamically populate a UI. Each key's value is a list containing an identifier int at v[0], and depending on the identifier, subsequent items at v[n>0]. The general format of this dict is as follows:

MenuItems = {

    'Title': [0], #Text
    '---': [1], #Separator

    'MenuItem 1': [3, { #Dropdown Submenu

        'SubItem 1': [2, 1000], #Submenu Items that return a value
        '---': [1],
        'SubItem 2': [2, 2000],
        '---': [1],
        'SubItem 3': [2, 3000]

        }],

    '---': [1],
    'MenuItem2': [2, 4000]

    }

I've written a recursive function to then traverse this dictionary and add the different menu items to the UI, however unfortunately I overlooked the fact that each separator has the same key name. As a result when the UI is built, only the first separator is shown in each UI level corresponding to the dict's level, like so:

Title
---
MenuItem 1
    SubItem 1
    ---
    SubItem 2
    SubItem 3
MenuItem2

Interestingly, and (for me) surprisingly, it is the first separator that is displayed in each UI level. I was under the assumption that as the duplicated key names overwrite each other from top to bottom, that it would be the last separator that would be shown, however it seems as though the first key's position is maintained, however it inherits the values of subsequent duplicate keys.

From reading up on python dicts further I understand that they may not be the best structure to use for data that is order-dependent (as is a UI builder), however their legibility and ease of iteration via for k, v in dict.items() means that ideally I'd like to continue with them if possible, rather than swapping to a list-based structure.

As renaming keys in a dict that's being looped over gives an error, to tackle the issue I've instead tried recursively iterating through each key in the dict and adding it to a new empty dict. The idea behind this is that for each entry in the original dict, its k & v is copied to the new dict one at a time, and if one of the duplicated '---' keys is reached, its name is changed to 'Separator ' + a count number. I'd then be able to use this new dictionary with my original function. Unfortunately I haven't been able to get this working and although the keys are copied and renamed correctly, again only the first separator key from each nested dict is included. The function looks like this:

old_dict = {#The same dict as in the original code block above}
new_dict = {}
global_count = 1

def prepare_dict(old, new):

    global global_count

    for k, v in old.items():
        if v[0] == 0:
            new.update({k:v})

        elif v[0] == 1:
            new["Seperator %s" % global_count] = old[k]
            global_count += 1

        elif v[0] == 2:
            new.update({k:v})

        elif v[0] == 3:

            new_dict = {}
            prepare_dict(v[1], new_dict)
            new.update({k:(v[0], new_dict)})
        
        else: pass 


prepare_dict(old_dict, new_dict)
print(new_dict)

This results in (where the commented lines are what I'd expect/hope to be included):

{'Title': [0], 
'Seperator 1': [1], 
'MenuItem 1': (3, {
    'SubItem 1': [2, 1000], 
    'Seperator 2': [1], 
    'SubItem 2': [2, 2000],
    #'Seperator 3': [1],  
    'SubItem 3': [2, 3000]}),
#'Seperator 4': [1], 
'MenuItem2': [2, 4000]}

Any ideas or suggestions would be very much appreciated, I have looked at a number of similar questions but none have quite brought me to the right answer yet. It seems like there should be a way to go through the raw dictionary line-by-line only while looking at the key at the current iteration and without the duplicated keys affecting their predecessors, but obviously I'm open to recommendations if there really is no way to achieve what I'm trying to do with dicts! Thanks :)