Hiking in Jungfrau Region-Best times

Look them up in AllTrails app. I just looked up one by typing in the hike. AllTrails will have the distance, route and usual times.

I meant what is the best time of the day to do these hikes. For example, is it better to do the Mannlichen-KS walk in the morning or in the afternoon? Same question for all other hikes.

It does not matter that much overall, but here is my opinion based on trail exposure and exposure of what you can see from the trail. I have not hiked all of those, but I am looking at the topographic map (https://map.geo.admin.ch/) to fill in the gaps!
Also, make sure to grab a picnic on some days!

1. Männlichen Station to Kleine Scheidegg: trail is sunnier in the morning, but does not matter too much otherwise
2. Grutschalp to Murren (and return): Why do this? The slow train does the same route, same view
3. First Station to Bachsee (and return): morning
4. Gimmelwald to Murren (and return): probably afternoon / late afternoon for best view of the Jungfrau?
5. Allmendhubel (top) to Pension Suppenalp to Pension Sonnenberg to Murren same, but this is so short, it does not matter much
6. Stechelberg to Lauterbrunnen (along the river): does not matter. Best for cloudy day
7. Schynige Platte wanderweg (circle hike): does not matter
8. Kleine Scheidegg to Eigergletscher Station (and return): afternoon / late afternoon, but this is not the most interesting hike. Too close to the mountain for a really good view, and the immediate terrain is barren (ski slopes)
9. Kandersteg lift (top) to Oeschinensee (and return): afternoon, definitely! lake is in shadow in the morning
10. Wengen Station to edge of cliff (and return): ???
11. Stechelberg to Berghaus Trachsellauenen (and return): does not matter (valley)
12. Kleine Scheidegg to Wengenalp: super short, 30 min. Probably best in afternoon

I've only done a couple of these:

1. Grutschalp to Murren (and return). Your view is to the east here, so afternoon would give you the sunlit views of the Eiger/Monch/Jungfrau. I did it in the afternoon but it was overcast. Morning, the mountains would be silhouetted. Consider taking the train one way and hiking the other, just for a different experience.

2. Gimmelwald to Murren (and return). This is a short, paved walk. Can be done any time.

3. Stechelberg to Lauterbrunnen (along the river). This was one of my most pleasant walks. Flat, paved, easy. Get off the main road and cross the river to walk along the west side. There are a few crossing points. I crossed at Trummelbachfalle, but there are others. You will walk along a paved (or at least well gravelled, I can't remember) trail that goes between cattle farms. I met and talked to a couple of farmers on this trail. I did it in the late afternoon and shade was starting to creep into the valley. You are deep in the valley floor here, so closer to noon will give you the most sun.

You did not list my absolute favourite Berner Oberland hike, which is to take the Schilthornbahn to Birg station, behind Grauseeli lake, down the Wasenegg ridge to Bryndli, past Spielbodenalp where there is a little cafe for refreshment, to Sprutz waterfall, where the path goes BEHIND the falls (amazing!), then either down to Gimmelwald, or over to Murren.

This site has some resources covering the hikes you mentioned, and a map where you can plot out the route I suggest: https://triptins.com/murren-to-gimmelwald/

Enjoy! You'll love it.

You might enjoy this book written by one of our forum regulars and her husband. If you have Kindle unlimited it is free to read. Otherwise, it might be a good investment.
https://www.amazon.com/gp/product/B09S8RQCSL/
Walking in Switzerland's Berner Oberland: Easy Hikes in the Jungfrau Region by Laurel and Richard Barton

We like to walk from Mannlichen to Kleine Scheidegg in later morning, so we arrive at KS around lunchtime. There is a little mountain restaurant with outdoor deck and great views into the Grindelwald area on your left, about 10 minutes before you reach KS. We stop there to enjoy lunch and the scene before continuing the walk down to Wengen.