AllSync & AllDup

I would like to remove files in a folder that all have a common text string within the file name. the text string 'thumbnail' is common to all files that I want to delete
Example:
myphoto-thumbnail.jpg
vacation2-thumbnail.gif
I have played with all manor of *thumbnail.* combinations but I cannot make it work. What should I do?

You only need a inclusive file filter with the text:

*thumbnail*

Also make sure the option "Ignore wildcards..." is deactivated.