I use both MS Word and Libre Office Write and when I set the Paragraph (¶) and other hidden symbol marks [ON] the word-space mark (middle-dot/interpunct) isn’t any character in my font. What am I missing to use a tiny middle-dot as when I use other PC provided fonts?
Just add the middle-dot glyph to your font — copy the period glyph, and move it up a bit, or use Complete Composites. The latter method will scale the dot down by 85% and move it to the middle of the Caps Height.
There is more explanation and how to edit CompositeData.xml in the Complete Composites Tutorial thread.
Since it is something that few will need to do, it is not included in the Help file, but the Help file includes links to the Tutorials Page, where you will find a list of links to tutorials on advanced features.
It is very user-friendly, so I think you can work out what it does. As with all code, syntax is crucial. Make backups before meddling with the file, which is found in the installation folder\Composites\ subfolder.