Description:
I'm using:
- Windows 10
- Keyboard for Guaraní Language
- LibreOffice 6.3

What I want to do?
While writing with the Guarani Keyboard on Windows 10, I can type the following characters by pressing AltGr plus the following vowels or consonants: a, e, i, o, u, y, g, as a result a tilde is added to these characters (ã, ẽ, ĩ, õ, ũ, ỹ, g̃). These keys combinations work perfectly with other programs (such as Firefox, MS Office, Notepad and Windows interface), only with LibreOffice they don't work. I mean: AltGr + g (to get g̃) and AltGr + shift + g (to get G̃) don't work in LibreOffice. When I press AltGr + g, I only get a standard lowercase g; and when I press AltGr + G, I only get a standard uppercase G.


What have I already done:

1. I thought, there was a problem with the font type:
But I have always written using Arial, Times New Roman, Verdana, Tahoma and OpenSans and never had this problem with any of the characters before. Besides that, I only have this problem while using LibreOffice.

When I copy and paste the characters (g̃ or G̃) from another text processor to LibreOffice and switch between the mentioned font types, the characters change as well keeping the special characters as expected.

What I think is the problem:
LibreOffice is not responding to the combination keys: AltGr+g or AltGr + shift + G, maybe because this combination is predefined to be used as a shortcut.

2. I went to Tools > Personalize > Keyboard-Tab and erased the shortcut asigned to the combination AltGr + g/G; Ctrol + Alt + g/G  AltGr + Shift + g/G and Ctrol + Alt + Shift + g/G). I saved this new setting and restarted the computer and LibreOffice. Result: The issue remains.

3. I tried to use Insert > Special Character >  Tilde (U+303). Result: By using this method  the combination is possible, but it presents an issue (tilde is oddly place or misplace even).

4. I uninstalled LO 6.3 and installed LO 4.4.0.1 and tried again using Insert > Special Character >  Tilde (U+303). Result: The combination works perfectly.

Conclusion:
1.  The problem may be that LibreOffice is not correctly responding to the AltGr + G command.
2. Characters (specially consonants) and Tilde combination (U+303) 
doesn't work well on LibreOffice as a result of a bug.

Before reporting this bug, a thread was open in the discussion forum not being able to find a solution. https://ask.libreoffice.org/en/question/205119/why-are-some-special-characters-not-displayed-when-writing-in-libreoffice/

Steps to Reproduce:
1. Using on Windows 10's Guarani Keyboard with LibreOffice Writer 6.3 (or Calc, Draw, Impress)
2. Press AltGr + g or AltGr + Shift + g.


Actual Results:
g G (g/G without tilde)

Expected Results:
g̃ G̃  (g/G with tilde - U+303)


Reproducible: Always


User Profile Reset: No


OpenGL enabled: Yes

Additional Info:
Before reporting this bug, a thread was open in the discussion forum not being able to find a solution. https://ask.libreoffice.org/en/question/205119/why-are-some-special-characters-not-displayed-when-writing-in-libreoffice/