@just_why The Easiest Solution is to Create different Profiles and Since you don’t want to Create different Profiles, You Should use Extension to Get this Feature Working
Watch the Video
01:19 You can see that you can add any Specific webpage to a Saved Folder Group Just by Clicking + Button
01:35 If Your Browser Profile window has Only New tab and if you Instruct Toast to open a Tab Folder Group, Toast will open all of those Saved Webpages in that Same Browser Window
But However If you Instruct Toast to open a New Folder Group while you have 1 or more tabs actively opened in a Browser Window, Toast will open the Saved Folder Group and all of the webpages Saved in it as a New Browser Window, You can See this Behavior at 01:47
(I did Every action Slowly So You can See What is happening and what I am doing)
Again at 02:07, I have Instructed Toast to Open a New Folder Group only while New Tab is actively opened on a Browser Windows, So Toast opened all of the Webpages Saved in that Folder Group on the Same Browser Window and while I Instructed Toast to open a New Folder Group while Few tabs were open 02:19, It opens the Saved Folder Group as New Browser Window, Hope You have Gained Clarity Now.
For Me, I have Strong Memory Power and Follow a Specific Browsing Pattern So I don’t need any Groups But this Should help with Reference of What You’re trying to Accomplish.