TempImporter makes it easy for you to try out assets before uploading them. It’s insanely easy to use!
When you open TempImporter, you get this GUI. You can use it to import a file or find a file that you imported
The list on the right shows the files you imported, and the button on the left allows you to import a file.
Importing files is insanely easy to do. Just type the name of the asset into the box on the left, click the button on the left and select a file. After you have done that, your asset should pop up in the list.
You can copy the ID of the asset (which is below the name of it) and use it as if you uploaded that asset.
Try it out here: TempImporter