An alternative to Jack's perfectly acceptable answer, this keeps the words but renders them slightly more meaningful and more grammatically correct. In full we would say 'show (the) assets (that have) not (been) exported'.

'Show not' immediately makes me think this is a bad translation that should read 'do not show' (As an English teacher I correct this type of mistake oh so often). In this context that could result in great confusion as 'do not show exported assets' is a valid possibility but not what you want to say, I think.

I think the first word should be "View", not "Show". That's Microsoft-standard. Just take a look at the menu in any application, like Internet Explorer.

Instead of "not export", it could be "not uploaded" or "unexported". To export normally means to export a file to another application on the computer. Upload means to upload it to a server on the Internet (opposite of download). Instead of upload, the word "publish" is sometime used. Which word is the best choice depends on what kind of software solution this is. The word "local/locally" can also be used, but "View local assets" can be misunderstood to mean assets in a local department, so it could be better to write "View assets locally" or "View locally stored assets" in the meaning of viewing assets stored on your local computer. I prefer "View locally stored assets" if you don't need to shorten it down.

Also, you should ask yourself if the computer will display all locally stored assets, or if it will display only the assets which is not uploaded. That should be taken into consideration when you choose a good string for the button.

Since you use the word "yet" in your explanation, I assume that this is a message to a user who wants to distinguish between assets that have been exported already and those that have not been exported yet. Above are two more alternatives, depending on your context.

"View" may be substituted for "Show" in any variant unless the difference is between "Show" and "Hide". In that case, "Show" is the more common alternative.

A note about "assets": It sounds odd to me. However, whether it is correct depends on what it is that the program creates. Out of curiosity, are you sure that these are "assets" and not "attributes"?