Add parentheses to expression lines and dynamics

Sorry to bother you again - can't find this in forums/issues. MuseScore 1.3, Win 7
How can I place hairpins, expression marks etc and dynamics in brackets (to indciate editorial additions)? I can't drag the accidental parenthses, and the only way I've found is to ccreate separate text boxes with the [ or ] in, and drag them to either end. This is very laborious, and I can't find a way of copying and storing the complete assembly for use elsewhere. Many thanks. (Please tell me if I've got the component and category boxes wrong)