Hello @yuberlin,
is it possible to use a hidden field in search form for itemid i manually
enter when making new menu item or new module an load it in templates
for building my custom URL?
Yes it's possible.
In your search, put all fields you need. Don't hide them if ou want to use this search in a page, and don't give them a live value.
Then when you create a new menu item for this search, in Advanced options of the menu, you can set and hide some field of your search form.
Same if you create Seblod List Module, you can set and hide some of fields.
Regards.
Lionel