Ligatures for single/double line separator?

[matype]

What

#114 (comment)

for 4+ ---- and ====

Why 4+?

#114 (comment)

For now, the three equals (===) are in the programming language operators so there is already a ligature and it does not extend to the full glyph width to be a separator line.
So a double-line separator is a ligature for 4+ =.