This technique allows adding Greek letters to most program’s text input.

1. See the Greek character chart. The row labels e.g. 03bx are the first 3 characters you type after the ctrl+shift+u you will see below. The last “x” value is the column of the table
2. press Ctrl Shift u at the same time, briefly
3. release all three keys
4. type the four-digit code and press Enter.

While doing this, you’ll see the character code until you press Enter, then the Greek character appears.

Examples of Greek characters in GIMP:

“mu” μ: Ctrl shift u 03bc Enter

“gamma” ϒ: Ctrl Shift u 03d2 Enter