Current assets don't display in Add an Asset modal for matrix field; using {owner.slug} in path For two channels that restricts uploads to subdirectory/{owner.slug}, when I want to add an image in an existing entry, the Add an Asset modal window doesn't list the existing images (this is a matrix field that supports multiple images). All other cases where the restricted directory isn't a dynamic asset folder work fine. I've updated Asset Indexes and Cleared Caches, but still no luck. Any idea what's up? Thanks.
It's because of how Craft resolves dynamic paths (paths with {variables}) in them. For freshly created Matrix blocks haven't been saved yet and therefore don't have an {owner} yet.

If a dynamic path cannot be resolved, then Craft will point it to a temporary folder that is unique per user per field, but, as soon as you save the Entry and the Matrix block has an {owner}, it will resolve to where it should and all the Assets from the temporary folder that were selected will be move to the resolved folder.

Any Assets that have not been selected will remain in the temporary folder. This also holds true for unsaved Entries if you're using {slug}, for example.