I have two major issues with the plan mode. The first one I already mentioned, the "planning night window" as imposed by the SeeStar is way too restrictive, you can do good imaging at least one hour before and after and there is no way to include that in the plan. This should be really trivial to change, probably just adjusting two constants in the code.
The second fundamental problem is that the planning works in absolute time. The start and stop times for every exposure are hardcoded into the plan and very difficult to change. You do not create these plans on the spot, you make them during the day, sometimes even many days in advance. There is no way to know for sure when you will have clear skies in advance, even with astro wheather predicting apps like Astrospheric, which I highly recommend. SO you prepare your plan for the 10PM to 2AM clear predicted weather window one day in advance, which turns out to be 1AM to 5AM instead - your plan is now useless. Two things are needed, a way to quickly move an entire plan or even parts of it around easily, if you want to shift a 10-exposure plan in time you have to manually change every single start and stop time right now, which is tedious and error prone.
Finally, we need a "start the plan right now" instead of the current rigid way of starting the plan at a given absolute moment in time. There is nothing more frustrating than setting up the S50, start the plan and then having to wait for 15 minutes or whatever until the plan actually starts. There should be a way to manually override the plan start time and shift everything forward.
There are many other ways planning mode could be improved and I have already mentioned some, like automatically creating plans for mosaics my covering a given area of the sky with exposures of a given duration, better support for plan reuse and multi-night exposures and so on. You can sort of do all these things right now manually but it is tedious and repetitive work which could be easily automated.
One other suggestion, I assume the plans are stored in some kind of internal data format, have you considered opening this to the users? For example, let the user create a text file with a sequence of RA/Dec coordinates, start and stop times and LP filter use and import that into a SeeStar plan. This would address a lot of my earlier suggestions with minimal coding effort on ZWO's part.
