[Bug] Tabgroup element generate different kind of event value after new Tab added

Type of Issue (Enhancement, Error, Bug, Question)

Bug

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Operating System

WIN10

PySimpleGUI Port (tkinter, Qt, Wx, Web)

tkinter

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Versions

Python version (sg.sys.version)

3.10.2

PySimpleGUI Version (sg.__version__)

4.61.0.206

GUI Version (tkinter (sg.tclversion_detailed), PySide2, WxPython, Remi)

8.6.12

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Your Experience In Months or Years (optional)

5 Years Python programming experience

10+ Years Programming experience overall

Have used another Python GUI Framework? (tkinter, Qt, etc) (yes/no is fine)
tkinter
Anything else you think would be helpful?
None

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Troubleshooting

These items may solve your problem. Please check those you've done by changing - [ ] to - [X]

• Searched main docs for your problem www.PySimpleGUI.org
• Looked for Demo Programs that are similar to your goal. It is recommend you use the Demo Browser! Demos.PySimpleGUI.org
• None of your GUI code was generated by an AI algorithm like GPT
• If not tkinter - looked for Demo Programs for specific port
• For non tkinter - Looked at readme for your specific port if not PySimpleGUI (Qt, WX, Remi)
• Run your program outside of your debugger (from a command line)
• Searched through Issues (open and closed) to see if already reported Issues.PySimpleGUI.org
• Have upgraded to the latest release of PySimpleGUI on PyPI (lastest official version)
• Tried using the PySimpleGUI.py file on GitHub. Your problem may have already been fixed but not released

Detailed Description

The event value of the TabGroup element is different between existing Tabs and new Tabs which is added by call method add_tab.

It should be caused by that the information of the new added Tab element missed to add into element.tab_index_to_key in method TabGroup.add_tab.

Code To Duplicate

import PySimpleGUI as sg

def tab(index):
    return sg.Tab(f"TAB {index}", [[sg.Text(f"This is Tab {index}")]], key=f"{index} TAB")

total = 2
layout = [[sg.TabGroup([[tab(index) for index in range(total)]], enable_events=True, key='TABGROUP')]]
window = sg.Window('Title', layout, finalize=True)
window['TABGROUP'].add_tab(tab(total))

while True:

    event, values = window.read()

    if event == sg.WIN_CLOSED:
        break
    print(event, values)

window.close()

Click each Tab to check the value for TabGroup element

TABGROUP {'TABGROUP': '1 TAB'}    # Key of Tab
TABGROUP {'TABGROUP': '0 TAB'}    # Key of Tab
TABGROUP {'TABGROUP': 'TAB 2'}    # Title of Tab

Screenshot, Sketch, or Drawing

Start with TabGroup.add_tab and the tab_index_to_key mapping identified in the issue, then run the provided tkinter reproducer. Done means selecting a tab added with add_tab reports its key consistently with the existing tabs rather than its title.