Lock Symbol in vROPS 6.0 Object Tags

When i saw this Lock Symbol in vROPS 6.0 Tags, then i was wondered what does this means? I haven't found an actual explanation for the lock symbol, but I'm fairly certain it is just to indicate the Pre-defined object tags

Predefined Object Tags

vRealize Operations Manager includes several predefined object tags. It creates values for most of these tags and assigns objects to the values.

For example, when you add an object, vRealize Operations Manager assigns it to the tag value for the collector it uses and the kind of object that it is. It creates tag values if they do not already exist.

If a predefined tag has no values, there is no object of that tag type. For example, if no applications are defined in your vRealize Operations Managerinstance, the applications tag has no tag values.

Each tag value appears with the number of objects that have that tag. Tag values that have no objects appear with the value zero. You cannot delete the predefined tags or tag values that vRealize Operations Manager creates.

Predefined Tags

Tag	Description
Collectors (Full Set)	Each defined collector is a tag value. Each object is assigned to the tag value for the collector that it uses when you add the object to vRealize Operations Manager. The default collector is vRealize Operations Manager Collector-vRealize.
Applications (Full Set)	Each defined application is a tag value. When you add a tier to an application, or an object to a tier in an application, the tier is assigned to that tag value.
Maintenance Schedules (Full Set)	Each defined maintenance schedule is a tag value, and objects are assigned to the value when you give them a schedule by adding or editing them.
Adapter Types	Each adapter type is a tag value, and each object that uses that adapter type is given the tag value.
Adapter Instances	Each adapter instance is a tag value, and each object is assigned the tag value for the adapter instance or instances through which its metrics are collected.
Object Types	Each type of object is a tag value, and each object is assigned to the tag value for its type when you add the object.
Recently Added Objects	The last day, seven days, 10 days, and 30 days have tag values. Objects have this tag value as long as the tag value applies to them.
Object Statuses	Tag value assigned to objects that are not receiving data.
Collection States	Tag value assigned to indicate the object collection state, such as collecting or not collecting.
Health Ranges	Good (green), Warning (yellow), Immediate (orange), Critical (red), and Unknown (blue) health statuses have tag values. Each object is assigned the value for its current health status.
Entire Enterprise	The only tag value is Entire Enterprise Applications. This tag value is assigned to each application.
Licensing	Tag values are License Groups found under Administration >Licensing. Objects are assigned to the license groups during vRealize Operations Manager installation. See Add a vRealize Operations Manager License Group.
Untag	Drag an object to this tag to delete the tag assignment.

Source:-

https://pubs.vmware.com/vrealizeoperationsmanager-6/index.jsp?topic=%2Fcom.vmware.vcom.core.doc%2FGUID-192AA550-0FDB-4E5D-9273-CA1D01F6562C.html