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It's just happened again. I'm going to have to uninstall until this is fixed.
Things have gone a little crazy the past day or two. Tabs keep shuffling about a lot. It seems that new tabs are counted as children of existing ones, and sidewise keeps trying to rearrange them according to hierarchy.

It would be good to simply have the option of disabling Sidewise's tab ordering functionality completely and just go with whatever order the tabs happen to be in. Is this possible?

Sorry, by group I meant folder. And yes - I've just tested and can confirm this is now fixed. Thank you!

I had a feeling that it may have been a Chrome limitation. Thanks for the info and quick response!