How can I set the left button of mouse as primary button?

I cannot find a way to do it using the many conf UI there are.
I may do it using the terminal and a command, but I do not what to use and in which file to put it.
Please, advise!

Hi lobaluna,
i use xinput.

To show the id number of your mouse:
Open terminal - “xinput”.
In the shown list you can see the id number of your mouse.
For example: ↳ Logitech Wireless Mouse id=11 [slave pointer (2)]

To list the settings of your mouse:
Terminal - “xinput list-props “your id number””.
For example: “xinput list-props 11”.
In the shown list you can see the number of some settings followed by their status (0/off, 1/on).
For example: libinput Left Handed Enabled (331): 0

To change the settings of your mouse:
Terminal - "xinput set-prop “your id number” “setting number” “status”.
For example: “xinput set-prop 11 331 1”.
Now you have left handed mouse enabled on.
But you loose this changings after rebooting.
For persitent changings the easy way is to add the last command to your autostart file.

In my case, because i dont like using scrollwheel for middle click, i enabled mouse left handed and middle emulation.
My last two lines of the autostart file:

xinput set-prop 11 324 1
xinput set-prop 11 331 1

Left handed greetings

I’m sorry to be absent. Very much thank you!

I figured it out before I read your post, @1666
I learned that xmodmap and a configuration file with
pointer = 3 2 1 4 5
is just enough in ~/.config/openbox/autostart file:

xmodmap ~/.mouseconfig

However, I see that your solution is more professional. Even I can use an alias to toggle the setting in case I get tired and decided to use the right hand (it happens ;D).

Thanks again!