Runescape custom windows

I feel like there should be a way to create custom windows which can have in them any buttons of your choice.

Being able to fill a window tab with prayer abilities, magic abilities, inventory space, equipment slots, and a chat box all in the same tab if you so choose to do so.

If you can just open every tab and have them all spread out over the whole screen to have instant access to all buttons, why can’t we just pick and choose which buttons we want to put them in a single window?

No, that just separates a window into multiple tabs which are still each their own preset windows.

If you put the Magic and Prayer tabs into the same window it has 2 tabs, but there should be a way to fill a single window with buttons from both the Magic and Prayer windows without needing tabs.