Optional character properties

In “CharacterProperties Service Reference” concerning com.sun.star.style.CharacterProperties some properties are specified as optional, among them CharKerning and CharKeepTogether. If I inspect an object supporting the mentioned service I find the Integer (specified: short) property CharKerning , though specified as optional, and I can assign a value to it. The effect gets visible. The boolean property CharKeepTogether is missing. Trying to assign a value to it raises an error displaying the expectable message “Property or method not found”.
What’s the reason for the difference?
How to create the optional property?

A follow-up question from How to detect non-breakable space when iterating document via UNO.

From searching the LibreOffice source code, it looks like CharKeepTogether is currently just a placeholder. It is impossible to create because there is no such property. Perhaps in past versions, it provided functionality similar to a non-breaking space.

For a property that doesn’t actually exist, the full description from CharacterProperties.idl sounds interesting.

This optional property marks a range of characters to prevent it from
being broken into two lines.
A line break is applied before the range of characters if
the layout makes a break necessary within the range.

Would it make sense to file a bug that the interface definitions need to be updated to completely remove the property?

I also looked in dialogs such as Format → Character → Position, which shows a checkbox for kerning but nothing regarding keeping together.

Now, Format → Paragraph → Text Flow → Do not split paragraph is ParaKeepTogether, and that functionality is alive and well.

Thank you! I feel a bit sheepish now, because you took that much trouble. My question was not about urgent needs but just for a better understanding of the implications of this question. Concerning that question I had the impression of a mix-up of the usage of any NO-BREAK-SPACE unichar (there are 3) with the absent CharacterProperty. I was wondering about who was entitled to “draw the option”. Developers?