If you'd just like to rewatch the LiMingHeart storyline, here are the timestamps. I didn't put them together but so far they seem accurate. They're based on the official GMMTV YouTube playlist.

Key For Breakdown: EPISODE.PART: TIME
LM = Li Ming's individual storyline
LH = context for Li Ming x Heart
unmarked clips are general interactions & sweet moments
1.3: 0:55-3:26, 3:26-5:13 (LH)
1.4: 0:22-5:11 (LH)
2.1: 6:39-10:00 (LH), 10:00-13:42
2.2: 5:07-10:30 (LM), 10:30-13:08
2.3: 5:10-7:03 (LM), 7:03-10:37
3.1: 6:36-9:51
3.3: 3:02-12:11 (LM), 13:38-15:40 (LH)
3.4: 0:12-1:50, 4:39-7:09, 12:41-15:34, 18:00-20:08
4.1: 1:16-4:00, 11:16-15:00 (LM), 15:36-20:46 (some LM)
4.2: 4:32-5:25 (LM not present)
4.3: 8:43-12:16 4.4: 0:12-5:10 (LH mostly), 9:18-9:37 (LH)
5.2: 1:42-8:54 (partial LM)
5.4: 1:58-12:54, 12:54-14:10 (LH)
6.1: 9:51-13:26 (LH), 13:26-14:34
6.4: 0:00-6:05
7.1: 15:29-16:16 (LH), 16:16-22:35 (LM, some LH)
7.2: 0:00-9:16 (LH but mostly w/o either present)
7.3: 7:56-9:21
7.4: 0:00-7:40 (LM)
8.1: 1:37-4:11 (LM not present), 10:13-15:29 (LM), 19:15-21:45
8.2: 2:23-8:16, 8:16-11:48 (LH)
8.3: 2:08-3:12
8.4: 0:00-2:48, 2:48-7:05 (LH, LM), 7:05-9:10, 11:25-13:04 (LM)