The sentence refers to how the visibility of property rows for skin attachments in the dopesheet and graph can be controlled by the tree view settings in Spine. Specifically, the "Show all skin attachments" setting in the tree view affects whether you can see the property rows for attachments that belong to skins other than the active one. When this setting is unchecked, only the property rows for attachments in the active skin are shown in the dopesheet and graph. If you check this setting, you will see the property rows for all attachments across all skins, regardless of which skin is active.
For example, if you have multiple skins with different attachments and you are working on animations, you might want to see all the property rows for these attachments to adjust their animations. By enabling "Show all skin attachments," you can view and edit these rows even if the attachments are not part of the currently active skin.
