At the top right of that column is an icon with three short horizontal lines. Click on it to show the button to "Pin" the column as a permanent column. (You can also pin and unpin it without having to re-create it from scratch.)
In the new pinned column, you can click the three-line icon again to expose a slide button. That opens entry boxes to add additional hashtags, so the hashtags for a particular topic can be together.
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