How can I type outline R symbol or outline form of any capital English letter in formula editor. The following shows the outline R symbol that I mean.
I am looking for a command or shorthand way of doing this (like typing rightarrow for → symbol).
You can use set R. That gives you the character as it is designed in OpenSymbol. If you want a different character, you need to get a font, that contains the character. Then you can use it as text or you can add it to the symbol catalog and refer it as any other symbol, e.g. %R.
Some of those open face characters e.g R, N, Z, Q are in the unicode block “Letterlike Symbols” and are supported by many fonts. The other open face characters are in the block “Mathematical Alphanumeric Symbols” starting at U+1D400. But even if you have a font, it is difficult to get them into the document. If you need such characters, you should look for a font, which has such glyphs at the position of the normal R. I see such glyphs e.g. in “MathJax_AMS” or “SF Math Open Face”.