Wow, now that is an interesting use-case
Discussion on the best approaches to scheduling with Node-RED come up fairly regularly and I think that the only thing we've ever been able to agree on is that there isn't a single approach that works for all.
Indeed, this came up again recently and I started to share some information about a possible comprehensive approach with Andrei but I don't think even that would be of that much help in this instance. Though it would have allowed you to build a custom interface for overrides. However, the approach I was looking at is very complex and needs a lot more thought.
It sounds to me as though you would be better off with a web page that displays the schedule for the day - I'd start with a standard base schedule, just one since you adjust it so much anyway - with an on/off override button. Then the 4 lines, each with it's own on/off setting, start time and duration.
On update, that could send the updated info back to Node-RED which would work out the output for schedex, bigtimer or whatever works.
So actually, thinking it through as a user journey lets us break the problem down into its key parts which is basically a web UI for output & input, a process to build a schedule and a node to enact that schedule.
It will probably not surprise you to hear me say that node-red-contrib-uibuilder would be ideal for building the web UI as long as you are OK with some simple web coding. Doubtless it is also possible to do with Dashboard as well. Though unless you need Dashboard for other things or are really not happy about doing any web coding, I think it would just be getting in the way.
You could also replace the web UI with a Telegram bot which means that you don't need to expose an interface to the Internet. However, such a bot would be fiddly to construct - though really it is just a different set of UI disciplines.
The good news is that, having broken down the process, you can see that the processing part would be similar no matter what the front end is.
Not sure if that monologue helps you at all but it was an interesting thought experiment if nothing else.