Looking at video, I think that would make sense to have same solo mode for subpanels of a modifier.
For instance, if user do a Ctrl click on expand icon of a Object Offset subpanel of Array modifier ; that should close Relative Offset subpanel.

A user preference setting would be nice that swaps the behaviour of ctrl clicks and simple clicks completely.

In D8042#194980, @ronan ducluzeau (zeauro) wrote:

Looking at video, I think that would make sense to have same solo mode for subpanels of a modifier.
For instance, if user do a Ctrl click on expand icon of a Object Offset subpanel of Array modifier ; that should close Relative Offset subpanel.

Good point. The code isn't really set up this way, so it's out of scope for this patch. But I'll try to remember to make this consistent in a future commit.

In D8042#195013, @Debuk (Debuk) wrote:

A user preference setting would be nice that swaps the behaviour of ctrl clicks and simple clicks completely.

In my opinion this is pretty far below the threshold for adding a new preference.

That's disappointing. I didn't know that there's a well defined threshold for that and hard to believe while looking at all these color values for themes in the prefs. The reason why I brought that up, was because there are quite some people who argued for a more compact layout for modifiers, like the modfiers addon, with a single modifier visible at a time. And with an option for the default behaviour to collapse all modifiers except the most recent unfolded one, you would have made a step to bring those back in. The people on devtalk are just representative for more users with that kind of preference.