We have recently switched to using YAML configuration and have the current pain point:

Area A has availableComponents: a1, a2, a3
Area B has availableComponents: b1, b2, b3

Area AB needs to have availableComponents: a1, a2, a3 and b1, b2, b3 (needs to merge availability from A with those from B)
Area AX needs to have availableComponents: a1, a2, a3 and x1, x2, x3 (needs to extend availability of A)

I have been able to use the !include as follows:

• Create a YAML file that only has a list of available components and then use !include to include it in various areas that need to use that same list

However, if any component needs to add even a single additional component (or merge two lists) I have not managed to make the !include work multiple times (to merge) and have not been able to add other components after the !include was used (to extend)

... so I had to copy and paste the list of components and add/modify as needed

I would appreciate your feedback if there's a way around this.