You can upload multiple apps / depots at the same time on Steam using this GUI I made in Godot Engine. It follows the principals of Official Steamworks GUI and uses Steam CMD to upload in the background.
For Wiki you can visit: https://github.com/rayzorite/Onyx-Steam-Build-Uploader/wiki or: https://mintlify.wiki/RykoTheDev/Onyx-Steam-Build-Uploader