Hello,
Regardless of the custom appearance style, this bug is present in v149 but not in v140esr.
Even before horizontal dividers were added, there was a problem:
if you hover the mouse pointer over the imaginary (or visible, if the fix from "Horizontal separator #611" has been added) horizontal border between the tab rows, the tab tooltip starts flashing several times per second.
If enough rows of tabs are open, you can encounter this effect very often when scrolling through the rows of tabs.

And another question is: what values can this parameter scrollbar-width: thin; have? I would like to make scrollbar it wider.
Thank you for supporting our product!
Hello,
Regardless of the custom appearance style, this bug is present in v149 but not in v140esr.
Even before horizontal dividers were added, there was a problem:
if you hover the mouse pointer over the imaginary (or visible, if the fix from "Horizontal separator #611" has been added) horizontal border between the tab rows, the tab tooltip starts flashing several times per second.
If enough rows of tabs are open, you can encounter this effect very often when scrolling through the rows of tabs.
And another question is: what values can this parameter
scrollbar-width: thin;have? I would like to make scrollbar it wider.Thank you for supporting our product!