I would like to launch such an extension that permanently connects me with an internal SIP number, e.g. 200, with a given telephone number.
I see it this way:
I run the script - how? via API? or maybe from a PHP server in asterisk? (I don’t know yet) with the given number.
Asterisk from the fixed extension dials the call to this number and at the same time calls the given SIP / extension.
So that after lifting the handset by the extension number you have established connection:
SIP (internal, e.g. 200) with a given external number via a given access number (TRUNK).
How to realize it?