Once it is already laid down, I don’t think so, but I may be corrected.

My method is to list all the track widths I want in the Board Setup > Predefined Sizes then use hotkeys W & Shift + W to scroll through them, observing the current size in the top LH corner. I then assigned a hotkey to the function “Change Track Width”.

This then means scroll through the list of widths to find the one you wish to use, move the mouse pointer along the track (no need to click) and press the hotkey at each section under the cursor. Changes are as quick as you can move the cursor.

Works well for neckdowns if you can’t be bothered writing scripts.

For new tracks you wish to alter the size as you lay, Left Mouse click when you wish to change, select new width with W / Shift + W, and keep laying.

There are other more “automatic” ways using Net classes, but I’ll leave you to learn that another time