An optional list of tags to apply to the Solid, separated by spaces. This is referenced by the Set solid collision filter action, allowing collisions to be enabled and disabled with different sets of solids.
Set solid collision filter
Enable or disable collisions with the Solid behavior according to tags. Specify tags using a string of space-separated tag names. In Inclusive mode, collisions are only enabled with solids that match any of the given tags; if no tags are specified, collisions are disabled with all solids. In Exclusive mode, collisions are disabled with solids that match any of the given tags; if no tags are specified, collisions are enabled for all solids (the default).
For each objext on layer a, set solid tags to "a", ect.