How can I combine two fonts in one automatically, so glyphs that are not available in first font, but available in second one can be merged into first font?
This is an easy task with fontforge.
First, you want to open the font with the missing glyphs and select
Select the font from which you want to pull glyphs. You will be asked whether you want to keep the existing kerning; you most likely want to select
The missing glyphs should be added in a few moments: