Condition tree.rootLineIds with multiple id's possible?

I didn’t get it work otherwise than using the following workaround by using an or operator and using two conditions:

[{$} in tree.rootLineIds || {$} in tree.rootLineIds]

I didn’t found a solution to get it working by using commas [{$foo}, {$bar} in tree.rootLineIds].

At least in the documentation, there is no example, what would match (see: So I guess, your approach is correct.