On Windows, try Ctrl+Shift+X to toggle between Left-to-Right and Right-to-Left in a <textarea>. Does that work on yours?

Yes, It's working well, thanks for your help, appreciate that I wish it was same as other browser, but it's good too

Firefox uses a lot of key modifier combinations for specific commands, so you could easily trigger a feature that only depends upon specific modifier keys. E.g. Ctrl+Alt+Shift+I is reserved for the browser toolbox (part of the developer tools).

In Windows you can also rotate the keyboard layout via such a combination (Ctrl/Alt+Shift), so you can accidentally switch to another layout without realizing this if you have multiple layouts installed.

Thanks a lot Ctrl+Alt+Shift+I not work in my Firefox I'll use your guide, thank you so much

Another way to switch text direction :

Type in the address bar about:config and press Enter (ignore the warning)

Type in the search bar and look for the preference :

bidi.browser.ui and set its value to true.

Then close and restart Firefox.

From then on all you have to do in a text area is press the key on your keyboard with the three horizontal lines (on the right side, next to "AltGr) and choose "Switch Text Direction".

The keyboard shortcut Ctrl + Shift + X , as suggested by jscher2000, works even faster, though.