Use timeline for a custom task list and custom content type

Question

Good morning fellow Sharepointers !

I have a big question in my head :

What i did :

I have created a custom Content Type -called Actions -, child of Task content type. SO it herits from Task's columns. I have created a new Task List and added my Actions CT.

So this Actions CT uses new dates columns (like "initial deadline" or "rescheduled deadline") and no more "Beginning", nor "deadline" columns.

Everything is well, i've sat up my views like "late actions","incoming actions" etc...

What is my problem :

BUT when i want to add a new Action to my Timeline, Sharepoint yell at me to verify if my action do have dates !

What i found :

By doing some tests, i have found that perhaps the problem is that Timeline does refer to "Deadline" column to create a marker, and to "Start" and "Deadline" column to define a range of time.

What i would definitely like to do :

I would like to use actions created into this task list in my timeline, so how could i achieve that ? Where could i define that Timeline uses my own custom dates columns instead of standard sharepoint ones ?

The other solution i've found should be to edit the existing columns, but it would modify it for ever. i would like to keep them clean if we ever need them...

--- EDIT ---

After @HarryB commented that this solution should be the one, i've tested it :

1. Creating a new Site's Content Type, inherinted from Tasks content type
2. Call it "test Actions"
3. Click on "Deadline" (in french "Échéance"), to modify its label.
4. Get the Column informations, and the only ones i am able to modify for that specific content type :
5. After clicking on "Edit columns properties", I can finally edit the label and every property of that date column. you can see here that the "Existing groupe" is the "Tasks and main problems columns".
6. After the warning pop-up, i'm going to see the default task list existing on my SP, that i never add any custom Content types. And....

The default columns has been relabeled everywhere. So this appears to be a wrong solution. Thanks to @HarryB though, he gave me some time and reflexion!

---Edit's end ---

I don't know if i'm clear on this, so don't be afraid to tell me an ask for some more information.

Thanks a lot to help me and have a nice day !

Answer 1

This is what I have tested and it works for me:

1. Create a new content type inheriting from Task CT
2. Create a new Out of the box Task list and add my custom Task CT to that list
3. Make it the default content type
4. Go to list settings and click on the due date column and rename that to Deadline.
5. I can add tasks to the timeline
6. My Due date column in the custom Task CT was not affected by the rename- the name change is only limited to the list