You can do it via variables, as shown here:
However using Edit > Find and Replace Text... with the "Search all layers" checkbox active is the quicker/pragmatic alternative.
Thanks so much Stephen.
I converted a Text box to a Smart object.
Is possible to turn it back to a Text box? (it's an old file so can not be undone)
On a relatively new version of Photoshop, you can use Layers > Smart Objects > Convert to Layers
On older versions, a script can automate decomposing a SO back to layers (where possible), search for Unsmart Object scripts on the web.
I tried to Convert To Layers and it's way #2. Is it possible for way #1?
Double click to edit the smart object. Does it open up a new .psb file window with an editable text layer?
Yes, it's an editable text layer
Is that a warning triangle on the font layer? Is the font missing?
Once resolved, unsmarting the text layer should work as expected. One can always drag the text layer from the psb file to the original doc, or use layer duplicate and select the original doc.
Same idea, but here is the problem. We have to relocate the Text box, and it's a huge amount of work.