Font Forum

In the picture, selected glyph has no code-point (as we can see in the glyph's properties and glyph overview panel) but it has a custom name and it is the combination/ligature for the two glyphs marked with ellipses. Both marked glyphs have code-points $0915 and $0937. The question is, how to add a glyph without code-point for ligature or composite, just with a custom name, like the selected glyph in the picture.

Within FontCreator, open the OpenType Designer. From there select the script that corresponds to the characters. If it is not available,m add it through the [+] toolbar button at the upper right.

Then select or add the Standard Ligature feature (liga). And then select or add a Ligature substitution. From there add a new item with the input characters and the output glyph.
And for Devanagari:

Your reply described the process or setting of ligature substitution. My question is how to add a glyph without code-point which I can edit or see in glyph overview panel and add that as a output glyph for the ligature in OpenType designer windows.

Waiting for your response, and thanks in advance!

From the main menu, select Insert -> Glyphs. Then you can provide a glyph name.