Instead of hanging a variable, I suggest you double-click the variable (or expression) and press Ctrl + Shift + I , it will bring up an Inspect Variable popup that you can change (and it will remember the size the next time you reopen it). Press Esc to close it (or click outside the popup).
Not as simple as hovering over a variable, but the next time you make this combination with a variable (or expression), a popup will open with a new size.
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