1. Open any document with multiple layers
2. Select a non-text layer from the Layers list
3. Press Cmd-C to copy the layer
4. Select the Type tool and create a new type object
5. Double-click the type object to enter input mode
6. Press Cmd-V to paste
If you try to paste the copied content of a non-text layer into a text field, nothing should be pasted.
A filesystem path to the layer that was copied is pasted into the text field, e.g.
This also happens if you try pasting into a UI text field, e.g. the Hex Color field in the Colors window./var/folders/qr/phpl6gzj6_71qbg9k79vgzxr0000gn/T/com.pixelmatorteam.pixelmator.x/9387B656-104B-4233-ACE3-0AC909808F33/Sample.tiff