懂
JLPT HSK 2

dǒng
Left: feelings 忄, right: supervise, director 董 (To make plants 艹 heavy 重, they must be supervised/monitored.) [heavy 重 = A vehicle 車/车 with double wheels 二 is for heavy loads.]
Only if you can supervise (control) your feelings, you will understand.

	重
JLPT HSK 3

chóng, zhòng
A vehicle 車 (= A hand-cart viewed from above: axle 丨, loading area 日, two wheels 二) with further wheels 二
A vehicle with double wheels is suitable for heavy loads.

	董
JLPT HSK 6

dǒng
Top: plant 艹, below: double, heavy 重 (vehicle 車/车 with double wheels 二)
(Breeding success is labor-intensive:) To make plants heavy, they must be supervised.

	熏
JLPT HSK 6

xūn
Top: variant of double/heavy 重 (vehicle 車/车 with double wheels 二 for heavy loads), below: fire 灬
The heavy vehicle is burning: It smokes!

	踵
JLPT no HSK

zhǒng
Left: foot 足 (knee cap 口 and footprint 止), right: double, heavy 重 (vehicle 車/车 with extra wheels 二 for heavy loads)
When you are on foot and that vehicle is heavy, it's easy: to follow.