In the edit box's context menu, along with the usual copy-paste functions and others like "Unicodify selected", a "convert case" option will be useful along with sub-menu options such as "Sentence case", "Title case", "All lowercase", "All uppercase", etc.

Edit: FYI, Libreoffice provides such an option under the Format menu as "Change case". The provided options are listed as:

• Sentence case
• lowercase
• UPPERCASE
• Capitalize Every Word
• tOGGLE cASE

Thanks.