Firefox 68.0. Apologies in advance if this question / "Issue" has already posed.
Very often when I am in a tab group and I close a tab (not the last tab in that group -- i.e., I don't believe that this Issue is this is related to Issues https://github.com/Drive4ik/simple-tab-groups/issues/209 | https://github.com/Drive4ik/simple-tab-groups/issues/289 | ...), STG switches to another tab group.
It's annoying and worse, I often forget which group I was working in (I have many groups with many tabs in each).
Here's a list of installed FireFox add-ons.

Here are my STG:

... and here are my STG preferences:

Hi! There was no such bug before.
Please, try it and write here if the error is repeated

Thank you @Drive4ik -- although I only very recently (a few days ago -- this week) installed Tree Style Tab.
I'm not sure, but on first glance I think that the TST setting that you indicate in your screenshot (above) may help resolve the Simple Tab Groups issue, or point to the underlying issue! :thinking:
Perhaps the combination of the two add-ons with those preferences appears to be 'needed.'
If so, I wonder: is the TST add-on setting indicated in your screenshot, above, changing a Firefox about:config setting? I previously looked in about:config (focusing mainly on browser.tabs settings) in regard to this issue, and I did not find anything obviously relevant, except (perhaps) the legacy/residual old tabmix (TabMixPlus) entry.

BTW, I really like this add-on (STG) -- really fabulous and very useful to me. Very intelligently implemented! Thank you, again, for responding to this issue! :+1
Thanks!)
Tab Open / Close Control addon had problems with my addon in the past and more than once.
People wrote that when it was turned off, the problems in the STG disappeared.
This add-on does not take into account the tab option hidden since it has been done for a long time and at that time there was no this functionality in Firefox.
Tab Open / Close Control addon page:
Last updated
2 years ago (Oct 27, 2017)
I wonder: is the TST add-on setting indicated in your screenshot, above, changing a Firefox about:config setting?
It seems that more addons can not change about:config page settings.
Now all add-on settings are stored elsewhere. At first it was a json file, now it is Indexed DB.
Good to know (re: Tab Open / Close Control). :wink: Thank you -- I'll uninstall it, and see if that helps. :smile:
Update 1: after a couple of days with the Tree Style Tab setting referenced above by @Drive4ik and each of the following add-ons disabled, Simple Tab Groups appears to be working fine, re: this "issue" (#455). :grin:
Update 2: I waited a few days to see how STG responded with the tab add-ons (above) disabled, then I re-enabled Focus On Left Tab After Closing.
After several additional days usage, I can report that the Focus On Left Tab After Closing add-on appears to work well with Simple Tab Groups. :smile:
However, the Tab Control add-on (tested separately) causes issues with Simple Tab Groups, per my original issue.
Summary
Add-ons compatible with Simple Tab Groups:
Focus On Left Tab After ClosingAdd-ons not compatible with Simple Tab Groups:
Tab ControlTab Open/Close Control
Most helpful comment
Update 1: after a couple of days with the
Tree Style Tabsetting referenced above by @Drive4ik and each of the following add-ons disabled,Simple Tab Groupsappears to be working fine, re: this "issue" (#455). :grin:Update 2: I waited a few days to see how
STGresponded with the tab add-ons (above) disabled, then I re-enabledFocus On Left Tab After Closing.After several additional days usage, I can report that the
Focus On Left Tab After Closingadd-on appears to work well withSimple Tab Groups. :smile:However, the
Tab Controladd-on (tested separately) causes issues withSimple Tab Groups, per my original issue.Summary
Add-ons compatible with
Simple Tab Groups:Focus On Left Tab After ClosingAdd-ons not compatible with
Simple Tab Groups:Tab ControlTab Open/Close Control