Find files

is it possible to 'find files' using more than one 'name matches' at the same time (i.e. multiple extension search), or - if not - can that be implemented?

Of course! Check out the find utility..

Multiple extensions can be done using wildcards.

Find Files panel: *.(jpg|gif|png)

The Search field uses Windows Search format, which I don't use enough to know off the top of my head.

For more complex cases, use the Find Files panel's Advanced mode.