double click a windows title bar to fill not working

Is this with any app, or specific ones?

I've noticed this on Sequoia 15.3.1 and 15.3.2, specifically with Firefox. With "double-click title bar" set to Fill, Firefox does noting. If I drag the window up to the menubar, it will maximize (I have that set, too).

I think it might have something to do with what the individual app considers a 'title bar', since after checking some of my 3rd party apps it seems the same behavior happens with Discord, as well.

Using Firefox.on Sequoia 15.3.2

Double Click the Tile Bar of Firefox

In my case will make Firefox Full Screen Mode

Using Safari on the same machine and Double Click the Tile Bar

Will Only heighten Safari up to the Main Menu Bar and expand down to in level with the Dock

OP's issue seems related to the Street Light Green Button and the effects that appear to me missing for some unknown reason

Check your setting

What have you got them set to ?

" Double-click a window's title bar to >> ??

Tested using Sequoia 15.3.2

Does relate to that

Options for arranging windows on Mac (gre… - Apple Community

Works here on three different Apple Computers all running Sequoia 15.3..2