Free text lines can be used to add descriptions for just about anything.
Note: Free Text Lines should be seldom used and cautious in their use, especially in Subhires as they cannot be allocated to equipment lists. An equipment list full of free text lines is no more useful than a list of equipment written on a piece of paper.
This can be done by selecting the edit/hotkeys button and selecting Insert free text which will place the new Freetext line at the currently selected position in the list.
This creates a new Freetext line
You can now overwrite the line with the description you require