In the MathType, choose Preferences→Cut and Copy Preferences: set MathML or text bullet, LaTeX 2.09 and later, uncheck all the check boxes.

We want to add two new buttons that run MathType formula editor (supposed installed).

The first one, inserts

*$formula$*inline: it opens the MathType, then the formula is manually written and copied to the clipboard, and MathType is closed; then the formula is inserted between the dollar signs.The second one, inserts labeled and numbered formula in the equation environment.