My export presets requires long names for differentiating them. So currently I can not read their names completely. This window is also not showing the complete names when the cursor is on the related preset.
Could you please make the width of the presets window on the export dialog adjustable?
I think you're referring to this dialog?
Unfortunately, while you can adjust the size of this dialog vertically, as you've observed, you can't adjust it horizontally. And LR doesn't show the complete name of a preset when I hover over it, either.
I think Rikk was referring to the main left and right panels of LR, which are adjustable horizontally.