Multiple File Manager

To efficiently organize files, eliminate duplicates, declutter your system and, ultimately, make room for new items, you need a file namer and duplicate finder that are capable of making this happen by following the set of rules you provide.
Multiple File Manager is a clear-cut application with simple, straightforward options that tries to meet both challenges. It has intuitive settings for renaming multiple files at the same time as well as for file management via duplicate removal.

Rename files and delete duplicates

Setup isn't necessary, so you can unzip the downloaded package and just double-click the .exe to reach the main app window. You're welcomed by a clean interface where all options are visible in one window.
To get started, you have to specify the full path to the target folder, in order to apply modifications to all files inside. Sadly, there is no button available for using a built-in file browser so you have to manually set the path.

Delete, replace or insert characters to the filenames

In the following step, you can choose between renaming and duplicate removal since it's not possible to rename as well as remove duplicates at the same time. The renaming part is almost identical to the one of Rename Multiple File, also made by this developer.
You can either delete strings of characters, replace specific text with something else, or insert prefixes or suffixes. The way files are compared to identify clone for removal is not clear but it seems that Multiple File Manager leaves the original file behind while getting rid of the rest.
All aspects considered, Multiple File Manager is a modest application that needs a lot of more work. As pointed out in Rename Multiple File's review, it doesn't previews for the new filenames or undo. On top of that, the comparison method for identifying and removing duplicates is unclear, making it dangerous when used on important files without first creating backups.