If you want to end up with /album/disc/files, the disc folders must already exist. The name is not important but a folder must exist. Rename does not create folders. To create folders you have to use a Move statement.

However if the disc folders already exist you can use the rename template in the attached image. It assumes that the Disc tag is set and consistent in each track. If that is not the case, replace Disc (Disc) with (Current Folder)

Note that you can test a template by the preview (eyeball) button while editing the template.

if only disc number is 1, or nothing
how to rename folder?

It entirely depends on the existing folder structure and what files are selected when your action runs. If there is no Disc folder or if the only Disc number is 1 or nothing, do you want to skip the Disc folder:

Anything can be done but I have to know what exists and what is selected. Do you always want the same structure (ie. a Disc folder) even if the disc is 1 or nothing? It's possible to create Disc folders with Move statements but there are too many unknowns for me to proceed.

Okay I think I get the uploaded image even though your action is not setting the number of Discs at the end. I can add that for you.

For an album without a disc in the subfolder, I would like to change it to artist/year/album/bitrate as before.

So basically this means that you want the album component renamed to the same pattern as in the uploaded image ... without the trailing Disc count. If that right? Or do you just want the album name?

If that's the case I can go one of two ways depending on the folder containing a track is of the form Disc #. When there is a DIsc folder should I leave it as is or rename it to be sure?

The answers to these should let me get it done.

Download the action at:

https://2manyrobots.com/actions/groove1027-Rename.zip

After importing you'll have an action named groove1027 Rename. It will be in the Action Manager and on the File>Rename>Actions submenu.

It treats both cases different. Note that the CD count reflects the number of existing Disc folders and is not based on Disc Count.

Please test both cases.