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:

[{$page.id.blog} in tree.rootLineIds || {$page.id.pressReleases} 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: https://docs.typo3.org/m/typo3/reference-typoscript/10.4/en-us/Conditions/Index.html#tree-rootlineids). So I guess, your approach is correct.