Here is an idea you can vote for if you would find it useful as well – https://ideas.powerbi.com/forums/265200-power-bi-ideas/suggestions/13219620-duplicate-measure-and-format-copy
So we end up copying the formula from text in the formula bar
And click new measure and Paste it into the formula bar
But 8 of 10 times nothing is pasted (at least when I select) – WHY ???
This is a strange user experience. But regardless, I find it odd that you can’t copy a measure definition. If this is odd to you as well, upvote the Power BI suggestion.