Beam spells behavior.

[Mithril]

I'd say the extra confirmation is what's undesirable.

No extra confirmation compared to today. Current users does not have to change anything compared to currently if they prefer the current curtailed beams. Today, using the keyboard you select a target and press Enter. The same in my proposal. With the addition that if you instead press some other key instead of Enter, say End or whatever, then the beam continues as long as it can. Nothing lost, no difference if you do not want to, functionality gained.

[Grey]

Learn to use the mouse - it's very liberating :)