The search bar on the left-hand side will only search in the body and title of the tickets in the current ticket filter.
If you want to find tickets based on other fields, it is best to create a filter with the correct fields selected and then search.
For example, if you want to search for a ticket which has a Office location as a custom field, you can first create a ticket filter which only displays tickets with that custom field and then search for the specific ticket.
If you want more information about ticket filters and all the options you can find it here: https://www.lansweeper.com/kb/347/configuring-and-using-ticket-filters.html