1.again-there we go: do NOT put all your now planned trips in it-just wait til the day-as it is bound to change in between. The RES, if needed at all, are all separate from that so do not interfere. Best advice is really to add trains really taken just before at platform or in hall-there may be hickups, strikes, changed plans, works on the line, delays (so that you can even catch a train that should have left) and so on.

We have seen dozens of sad reports from people on this forum who had a masterplan planned and saw it go down the drains and then had to forfeit traveldays.

2.On some lines service is so frequent that it does not really seem to matter (comparable to nr of trains over that famous bridge by StateRail in SYD), but it still has to. Pus that in general in the app you just have to choose what time-on the old paper one had to check more.

Here is some useful information from the experienced travellers in the Community regarding both planning, reservations and activation of pass and travel days. 

 Planning

The rail planner is normally not up to date, as it only is updated once a month, so to be sure of the time table you better check the timetable and availability on the websites of the national railways. The bigger national railways, like DB (Germany) SBB (Switzerland) and ÖBB (Austria) cover several countries. 

 Reservations 

Thanks for the information but it still doesn’t answer my question. I will give an example. Going from Zurich to Lauterbrunnen via Interlaken. Probably take the 8:02 train from Zurich.  Have to buy tickets from Interlaken to Lauterbrunnen as they are not covered by Eurail pass. Will them return to Interlaken and take train from Interlaken to Zurich via Lucerne. The problem is I do not know what time we will travel from Interlaken to Zurich as it depends on how long we spend in Lauterbrunnen and Interlaken. So I have started using my “Travel Day” when we left Zurich, but do I need to decide before we leave Zurich on what trains we will be coming back in the afternoon, or can we jump on any train back (as we will not be reserving seats for this day).

You add the journey with your train to your Trip and then connect the journey in your Trip to your pass just before boarding the train when you know what train you will travel with. 

You never need to decide any travels in advance, unless you need a mandatory reservation. And the advice is to never activate a travel day in advance.

If it helps just consider your trip as a diary where you can add or remove trains at will at any time before travelling.

You could for example put a train at 1000 from a to b on 1/1/2023. On the day you realise you can catch a different train at 0900. You simply delete the 1000 train and add the 0900 train. Then just before boarding the train you activate the slider in your trip which creates a travel day and adds the specific train to you travel day QR code. 

If you then leave that train and decide to continue to station c at 1400 you simply add that train to your trip. operate the slider for that train and your pass now shows both trains with the same QR code.

You can amend your trip as many times as you want, and even if you have added a train to your pass and then decide not to board it you simply slide the bar back to remove it from your travel day, and if you want add an alternative.