Total Commander

that would be a nice thing if TotalCMD had a SD card usage plugin just like the tool in Astro Explorer. If someone doesn't know, it shows storage usage per folder / file, you can also enter folders to see subfolder usage.

would it be considered?

Just add a button (using the button with the green plus sign) with the following settings:
Function type: Internal command
Command: Click on >> and choose command Nr. 115