Just to complete, what I did as well.

I checked the file containers.json in my profile. There I find a totally different sorting of the entries than in about:preferences#containers

Thanks

An extension like MAC can also store data in its extension storage (indexedDB; storage folder in the profile folder). This data usually gets stored if you uninstall an reinstall the extension, so you can try this in addition of renaming containers.json.

Thanks a lot @cor-el

Unfortunately there is no adequate data in the folder indexedDB to check.

Also further attempts to change the file containers.json failed. After changing this file it appears that Firefox automatically recreates it, my entries are in a different order, partly present, partly not present and partly duplicated. Also not wanted entries were added.

Is there a special procedure that the file containers.json is taken over as I created it ?

You did made sure that Firefox wasn't running when you removed containers.json ?

• "3-bar" menu button -> Exit (Power button)
• Windows: File -> Exit

Unfortunately not, cor-el

Sure, I closed Firefox before doing changes at containers.json file.

In the meantime I was able to make a sorting by moving the entries at the extension setting 'Manage Containers', but this sorting is not adopted. When I open a new tab or click on the MAC icon in the address bar, I get a totally different sorting of the entries.

I tried to sort the entries with containers.json file, but the sorting changes automatically, some of my entries will be lost and some duplicated, as well some default entries will be added. Is there no way to overtake the sorting which I mentioned and did before in 'Manage Containers ?

Thanks