Your comments

Thanks very much for the reply.

I do not think this will improve the existing solution (the triple `$`), which is already very convenient to use if we edit and convert markdown always in Haroo.

Sometimes I need to edit markdown file by Haroo, and then use these files as the input to other converters, like Pandoc, to generate customized HTML for my website. The problem is Pandoc use just a single `$` for the inline math expression in LaTeX. This is also, as far as I know, a convention in scientist community, where people are fund of using LaTeX in markdown and seldom care  about the currency unit use of '$'. 

So my suggestion is to supply an option for user to switch between the two delimiter: the triple `$`, or the single `$`, for the inline MathJax expression. 

Thanks again.

It occasionally happened in my PC, too.

Have you tried to click the icon in the task bar (although nothing shows on the screen), followed by keystroke  `alt+space`, after that a menu with the option `Maximize` will appear, and click it?

It works for me.