• Blender Version 2.80, 2.81 - Not tested with other versions.
• Batch-Imports Mixamo-Animations without (!) skin from Fbx.
• Renames the actions according to Fbx-Filename.
• Can Batch-Save individual animations as Blendfiles.
• Also can Batch-Export animations as ESCN-Files,
• using the Godot-Blender-Exporter (Has to be installed).
• Doesn't remove the 'MixamoRig:' prefix from the Bone-Names, yet.
• Can't yet pack animations in a single .blend/.escn
• Doesn't work with meshes currently, only bare armatures with animations.
• Can't join animations in a single file, yet.
• Only work's with Fbx-Files.
• X, Z locations get removed completely from the Hip-Bone (!)

0. You might want to replace spaces in the filenames (optional)
1. If you downloaded a Mixamo-Animation-Pack move the .fbx with the Model/Skin to a different location! (important)
2. To see printed warnings/errors logs, open Blender in Terminal
3. Open a new file in blender and save it in the directory, with the files you downloaded from Mixamo. Working-Directory. If the Blendfile contains objects (default-cube or a model, camera etc.), the script will backup the file.
4. Open the script in the Text-Editor.
5. Change the Option-Variables True/False, for what you need.
6. Run the Script, done.

When you've exported to .escn you can:

cd your-anim-folder/escn_out

godot -e

cd your-anim-folder

for foo in *.fbx; do mv "$foo" `echo $foo | tr ' ' '_'` ; done