In finder (10.5.1) you can Command+double click on the column separator to have them expand to show the longest name of the folder/file names.

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Just double-clicking the column sizer will "Right Size This Column" and option-double-clicking will "Right Size All Columns Equally," but I don't think there's an equivalent for "Right Size All Columns Individually," nor is there an option to always "Right Size" columns automatically when you navigate to them (I wish there was, too).

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I just tried these tricks.
In my case, option-double-clicking did "Right Size All Columns Individually" instead of Equally.
I wonder why...?

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