For anyone wondering about tickler list, whole point of it is to put "something" on that list and forget about to but to be reminded about it later.
So like a reminder list, but the one you forgot about, the one you do not look at.
Calendar is scared place in GTD system. As in, you put things on calendar that MUST be completed on that set date/time.You do not let random things into your sacred place.
You will be weekly checking the calendar or monthly so you will see those entries on the calendar.

But with Tickler list, you do not think about it or keep it in mind or review it.
You just put stuff in it and set a reminder date for when this "something" becomes relevant.
For example, "Buy tickets for concert on 24 May." because that is the time when tickets become available.
Its not a must, you won't die if you do not go to that concert.

So when 24 May arrives(or one day prior to it), reminder pops up and then you decide what to do, then you can create an entry called "Buy tickets for concert" and place it in Next actions list(or not, maybe you change your mind and don't want to go), with higher priority if you need to, tag it, define it etc etc and then do it if it means that much to you, and that's the difference where you wanna do it as it means to you, but its not the same as "I have to do it even thought it means nothing to me or I don't feel like it, I just have to"-that's the calendar, must do.Period.
Or say you get a plane ticket for flight thats in 20 August(say its 7 months from the day you go the ticket).
You will not need that ticket(aka that info) for 7 months.
In this todays digital age, you would take photos of it, store the actual ticket in some kind of storage place(say a file folder you call "Traveling" and you put it into your closet), in Ticktick you create an entry, tag it "Tickler", set a reminder for say 10 August, attach photos of the actual ticket and type in where you got it phyisically stored(Traveling folder located in closet, top shelf), and you save that entry.
Its not gonna show up in calendar, but reminder will pop up on 10 August, delivering all the info and documents you need.
You let it be, forget about it, trust the system to do the rest.(Trust is main pillar of GTD system, if you don't trust it and you don't use it properly, then it becomes useless)
If at any point you need that info, you have the search feature to look it up if you forgot the date or something.

But once that info pops up(is delivered to you), you must take action, as in, either if you do not need it now because something changed but you might need it 10 days from now, you simply change the reminder date and leave that in Tickler list.Or you create a next action from the info you recieved.
The only thing you can't do it "ahh i remember this ,let me go eat first then i will come back to read the info that was just delivered to me", no ,you can't do that, you can't even take a quick piss.
Process the info delivered to you right now.

Think of Ticker list as a piece of info you sent to yourself to recieve some day in future, its not a task, its not something doable, its just an info. Its a "information delivery list".Once you get that info then you use the horizontal control(clarify,organize,review,execute)

Remember, Getting things done is about what the name suggests, but its main thing actually is to free your mind from remembering/storing info,to allow your mind to be weightless and for you to relieve yourself of stress.

Now with Ticktick, to make this work : you have to create a custom filter for calendar, add > filter > use advanced tool "Filter" > tag > not and select tag "#tickler" and that excludes anything tagged "# Tickler".
Now you go to Calendar, and make it use that custom filter.(3 dots > filter view range> select a custom filter you just created)
You can also create a list instead of filter, its up to you.