Grouping of notes in irregular measures

I’m new to MuseScore.
In a score, I have a general time signature of 12/8. At one place I have one measure with time signature 10/8. I want to enter 10 eight notes in this measure, groupes (with a beam every 2 notes). ScoreMusice keeps grouping notes by 3 (as in the 12/8 measures). Maybe an example describes better the problem. I encountered this problem when I tried to copy (entering manually) the following sheet. My question is: how can I enter into MuseScore the 7th measure, lower staff.
Thanks for your help.