Vivaldi Tab Stacks

Hi, I am using the latest Vivaldi snapshot with two-level tab stacks. Vivaldi 3.6.2160.3 (Official Build) (64-bit)

Whenever I sign in all of my carefully made tab stacks disappear. As it is time-consuming to set up on the browser having them disappear is quite disheartening.

I set up Profiles for my kid's Homeschool which are arranged a by tab stack for them to easily follow and keep organised