Yeah, Tween behavior really lacks looping and reversing options. I posted this idea a long time ago:
construct3.ideas.aha.io/ideas/C3-I-647
You can simply run the second tween after a delay: Tween "increase_size", wait 0.2s, Stop Tween "increase_size", Tween "decrease_size"
Or I often use this simple effect:
On Clicked Button
Button set scale to 1.05
Wait 0.1s
Button set scale to 1