How can I edit an existing font?

Writing in Guaraní I need a certain character not available in unicode or special characters. I have been adviced to: edit an existing font to create the required character in the Private Use Area.

My dial-up internet and slow connection here don’t give me time to search this out in order to understand it fully. So i thought I would throw it out to you wizards.

Any help much appreciated.

This is not strictly a LO issue, however I can understand the need. I will see what I can come up with but cant respond for a few days.

Thank you.
I was told in Word it was Shft + tilde key followed by G. But dont have word to try this in, and want to keep to LO trying to stay off word.
Will await your responce in a few days.

Unfortunately, after futher investigation of this issue, it appears that the best option is to use a font prepared by someone with greater familiarity with Guaraní than myself. There is a san-serif and Roman font with the required precomposed characters prepared by Wolf Lustig and a selection of Paraguayan font options on the website of Luc Devroye.