Suppress "You can boomarks, reading mode, ..." popup

[krausest]

Avoiding this popup seems to be pretty hard. No flag seems to prevent it from showing.

[krausest]

What maybe (?) works is to create a user profile with a preferences file, which I put into ceb270b.
The user profile directory is deleted and recreated with the preference file every time the browser is restarted to avoid side effects due to the profile.

[syduki]

It may be a workaround with profile, but it looks cumbersome to me, moreover I think I found an easiest way how to disable it, at least I don't see it anymore.
Searched in the chromium source for text "You can open bookmarks", then follow the white rabbit did a search by that ID here then here, and finally found that nasty functionality triggered by SidePanelPinning feature, so we may just disable it with --disable-features=SidePanelPinning. Also, found another one here, IPH_SidePanelGenericMenuFeature which seems to be related specifically to that popup text, so this also works: --disable-features=IPH_SidePanelGenericMenuFeature.
Some couple of hours spent fruitfully, huh...

[krausest]

Yes, I know that pain 😄 + thank you!
I added the flag. Of course that's the better solution.