In what programming language to order a GUI?

Question

Programming languages

There is a project - several subroutines launched from one shell.
The shell is made in Python. It looks clumsy, the skin does not stretch, and other problems.
There are plans to order this shell on freelance.habr.com in another language.
In what language should I order it?

Requirements for the shell:
1) So that another programmer can later modify it relatively easily if there is no connection with the first programmer.
2) To look relatively "modern".

Main functionality:
1) Buttons that launch subroutines.
2) Fields filled in manually by the user, from which the data is saved to a text file in a specific format. When the values ​​in the fields are changed by the user, the file is overwritten and closed so that another routine can read this data. And vice versa, if another program writes its data to this file, read it and show it in the windows.

Answer 1

Qt.
Or competently on PyQt.
You can also use Gtk, but finding a new slave can be a problem.

Answer 2

C# / WPF (.NET)
VB.NET
Delphi/Lazarus also possible

Answer 3

Qt but it is somewhat peculiar, both in terms of programming and license. Net win form , wpf. Java who knows how to cook, it turns out well. As an option, electron