Populate a choice field with choices from four other choice fields in the same item

I have 5 choice fields in the same list:

[All_Choices] Multiple Choice

[Lease_Car] BMW, Mercedes, Mazda

[Transmission] Manual, Automatic

[Seats] 2, 4

[Upholstery] Leather, Cloth

The All_Choices field needs to be automatically populated to contain the user's choices from the 4 other choice fields in the same item e.g. [Mercedes, Manual, 4, Cloth] - as a list of choices, not as a string of the choices concatenated into a text field.

Can this be done by JSON column formatting or only with a Power Automate flow?

If it can be done just with JSON column formatting, could someone please send me the JSON?

If it must be done in Power Automate , could someone please send me the flow (also that avoids the recursive loop as its the same item record that's being updated by the flow).

Thanks!

Shane