It is possible, but (IMGDO) it’s harder than it should be.
In FoldingText, click on the File menu and select Open Application Folder. That will open a Finder window. Close FoldingText (may not be strictly necessary, but this didn’t work for me with FT open). Edit the ‘user.less’ file in another editor (TextEdit will do).
Add a line:
@lineHeight: @fontSize * 2.0;
Save and re-open FT. Should now be double spaced.
You can tinker with other settings while you’re in there; font face, size, background color, margins, etc. This is what I’m using:
// This is your user.less. Use it to override the default styling. When this
// file is first created all lines are commented out (start with //) and so it
// has no effect in the editor’s style.
// To change the font uncomment the following line:
// To change the font size uncomment the following line:
// To change the line spacing, uncomment the following line and change
// the value as desired.
@lineHeight: @fontSize * 1.75;
// To change the left and right margins uncomment the following lines:
// To change the base “ink” color (used for text) uncomment the following
// To change the base “paper” color (behind the text) uncomment the following
// Color used to indicate something. Such as when mouse is over a link.