This feature is not supported now.
As a workaround, you could pin some channels which you frequently use on the top of the page.
Besides, creating classifications for Microsoft 365 Groups maybe help.
I found a similar feedback in this link. You could vote for it.
Microsoft will always focus on customer’s feedback and experience. Some new features would be added to the services based on customers' feedback in the future, and your good ideas will be very helpful for them to improve the service.
Your time, understanding and cooperation will be highly appreciated.
If the response is helpful, please click "Accept Answer" and upvote it.
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