Since you seem to be using that symbol a lot, you might want to extend the font "standard" yourself rather than waiting for an update.
- Open the font file in QCAD (type: 'Font *.cxf', location: QCAD directory/fonts).
- add a block with name "[UUUU]" where UUUU is the hexadecimal Unicode for the character you want to add (e.g. "[02BB]")
- Edit the block to contain the glyph for that particular character. The height of a capital 'A' is 9 units, 0/0 of the block is at the lower left edge of the glyph.
- If you restart QCAD, you can start using your new glyph
You might want to consult the Unicode character definitions to find out the right Unicode for a small triangle: www.unicode.org