I’ve moved this to Galaxy Watch Studio Forum as that appears to be the tool you are using. For Buttons only the top layer is active any that are lower will not work.
For your tag expression A good thing to do is write it in text with each element distinct so…
([ba]<100) this is always one except for a very instant when it is fully charged.
([s]%2==0) the modulo operator will be 1 on odd number and zero on even numbers
so on odd numbers it shows and on even numbers it is off so it blinks every second.
It takes a few seconds after a watch face becomes active for everything to initialize that is why it takes two seconds.
I’d suggest you use a simple animation that is the color of the back ground that is clear then dark for 15 seconds ending on a clear panel. Since you never would know what second the watch face would start.
Samsung Developer Program