Here is a google post i found;
Tap the word “Flashlight“ below the icon to open the brightness slider. Alternatively, you can long-press the Flashlight icon itself to access it. Adjust the slider from Level 1 to Level 5 as you desire. After choosing a brightness levelFrom googling, tap Done to leave the setting.I found How to adjust the flashlight brightness on your Samsung Galaxy phone;
- Tap the word “Flashlight“ below the icon to open the brightness slider.
- Alternatively, you can long-press the Flashlight icon itself to access it.
- Adjust the slider from Level 1 to Level 5 as you desire.
- After choosing a brightness level, tap Done to leave the setting.