Hello,
Sorry to hear you are having trouble.
For a moment, forget about the tab renaming and order of the tabs, we just want to work on getting the grouping working.
Post the text of your save Group file with just a few entries (not hundreds). Example:
[Group]
GroupCount=2
GroupLeft=860
GroupTop=688
GroupRight=2804
GroupBottom=1509
GroupMax=0
Locked=0
[GroupyEntry1]
OwnerProcess=C:\Program Files\Mozilla Firefox\firefox.exe
NewTabName=2222222222
RunElevated=0
NoPatternMatching=0
CommandLine="--new-window https://www.espn.com"
WorkingDirectory=C:\Program Files\Mozilla Firefox
Target=C:\Program Files\Mozilla Firefox\firefox.exe
MatchingClass=MozillaWindowClass
[GroupyEntry2]
OwnerProcess=C:\Program Files\Mozilla Firefox\firefox.exe
NewTabName=BlaBla
RunElevated=0
NoPatternMatching=0
CommandLine="--new-window https://www.espn.com"
WorkingDirectory=C:\Program Files\Mozilla Firefox
Target=C:\Program Files\Mozilla Firefox\firefox.exe
MatchingClass=MozillaWindowClass
You will find the saved groups with this:

First, does this low tab count save group work, does it auto group when opened (try multiple times please)?
Sean Drohan
Stardock Support Manager