Mohammad,
However I cant quite see what you are trying to achieve, Are you trying to full screen a particular tiddler?
When running TiddlyDesktop as a local windows App I can use the window controls to make it full screen (Except for the top Application bar).
If what you are after is the items proposed in the pre-release of 5.1.18 I would imagin this needs to be released first, on a previous occasion, the updated TiddlyDesktop followed right away.
OR is there something else you are thinking about?
just trying to help.
Tony