I have a requirement to add two groups a menu column, i tried to do it on my own but i wasn't able to

please see the image below,

Currently i have 5 columns for the "Products and Services" and 5 menu gropes are assigned to it, however we don't have much content (menu items) under two of those groups, so i was thinking whether its possible to add two groups under one column ? and make total columns for "products and services" to 4, instead of 5.
in have noticed when you change numbers of columns (Ex: 4) but you have 5 Menu Groups, in that case it will assign 5 menu groups to 4 columns, but the issue is i can't control which are the two Groups should be in 1 column. is there a way to get this sorted ?
Please refer to the attached image, i have showed the way it is now with 5 columns, and also i have made a simulation (using photoshop) who it should be.
website : sisco.webs.lk
Please get back to me on this ASAP,
Thank you and Best Regards,
Thisara
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