You can search the content of loaded scenes via the Hierarchy window's search.
You can use various prefixes to narrow the search:
| Prefix | Filter description | Example |
|---|---|---|
t: |
Component type | t:Light |
ref: |
Objects that contain a reference to | By instance ID: ref:49092:By file: ref:"Assets/Example Texture.png" |
You can also narrow the search using the dropdown:
Unity, huh, how?