why glue points on MathType formula are invisible?

I want to use glue points and connectors in DRAW to show relations between variables in my MathType formulas. But all glue points become invisible after placement. What`s wrong with me or Libre? Everything is OK with non-OLE objects. Is it a reason for the problem?

There are a few bug reports related: maybe fdo#106621 the more interesting.

As a workaround, you can convert the formula to curves (menu Shape - Convert - To Curve), ungroup it (menu Shape - Group - Ungroup), combine it (menu Shape - Combine).

Add Answer is reserved for solutions.

Press edit below your question if you want to add more information; also can comment an answer.

Check the mark (Correct answer mark) to the left of the answer that solves your question.